Transcriber Note
To preserve cross-references between the volumes, both have been
combined into one. Text emphasis denoted by _Italics_. Whole and
fractional parts of numbers displayed as 123-4/5.
THE
Medals of Creation;
OR,
FIRST LESSONS IN GEOLOGY,
AND
THE STUDY OF ORGANIC REMAINS.
VOL. I.
"If we look with wonder upon the great remains of human works, such
as the columns of Palmyra, broken in the midst of the desert; the
temples of Pæstum, beautiful in the decay of twenty centuries; or the
mutilated fragments of Greek sculpture in the Acropolis of Athens,
or in our own museums, as proofs of the genius of artists, and power
and riches of nations now past away; with how much deeper feeling of
admiration must we consider those grand monuments of nature which
mark the revolutions of the Globe; continents broken into islands;
one land produced, another destroyed; the bottom of the ocean become
a fertile soil; whole races of animals extinct, and the bones and
exuviæ of one class covered with the remains of another; and upon the
graves of past generations--the marble or rocky tombs, as it were, of
a former animated world--new generations rising, and order and harmony
established, and a system of life and beauty produced out of chaos and
death; proving the infinite power, wisdom, and goodness of the Great
Cause of all things!"--Sir H. Davy.
[Illustration: _Pl. 1._
_J. Dinkel del. G. Scharf lithog._ _Printed by Hullmandel & Walton_
MEDALS OF CREATION]
THE
Medals of Creation;
OR,
FIRST LESSONS IN GEOLOGY,
AND
THE STUDY OF ORGANIC REMAINS.
BY
GIDEON ALGERNON MANTELL, LL.D. F.R.S. V.P.G.S.
PRESIDENT OF THE WEST LONDON MEDICAL SOCIETY, ETC. AUTHOR OF THE
WONDERS OF GEOLOGY, ETC.
[Illustration]
"Voilà! une nouvelle espèce de médailles, beaucoup plus importantes,
et incomparablement plus anciennes, que toutes celles des Grecs et des
Remains!"--Knorr, _Monumens des Catastrophes_.
IN TWO VOLS.--VOL. 1.
CONTAINING
Fossil Vegetables, Zoophytes, Echinoderms, and Molluscs.
SECOND EDITION, ENTIRELY REWRITTEN.
LONDON:
HENRY G. BOHN, YORK STREET, COVENT GARDEN.
MDCCCLIV
LONDON:
R. CLAY, PRINTER, BREAD STREET HILL.
TO
MY SONS,
WALTER MANTELL,
OF WELLINGTON, NEW ZEALAND,
AND
REGINALD NEVILLE MANTELL,
OF KENTUCKY, UNITED STATES,
This Work
MY LAST ATTEMPT TO PROMOTE THE ADVANCEMENT
OF SCIENTIFIC KNOWLEDGE,
IS MOST AFFECTIONATELY INSCRIBED.
G. A. M.
Chester Square, Pimlico,
_Feb. 3, 1853_.
[The above having been penned by the much-lamented author of the
"Medals" some months previous to his decease, it is retained in this
posthumous edition of his favourite work as an appropriate dedication,
dictated by the parental affection of one of the chief promoters of
geological science in England, and addressed to his absent sons, whose
works have already shown them to be enthusiastic labourers in the same
field, both at home and in distant parts of the world.]
PREFATORY NOTE TO THE SECOND EDITION.
The untimely Decease of the lamented Author of the "Medals of Creation"
during the progress of the present edition through the press has
unavoidably delayed its publication.
The First Volume has been wholly rewritten by the Author.
The materials of the Second Volume had been elaborately revised and
much enlarged by Dr. Mantell previously to his Decease. The Editor
has laboured to carry out the intentions of the Author in rendering
this part of the Work as complete a compendium as possible of the
Palæontological history of the Organic Beings of which it treats, and
in adapting it to the requirements of the Geological Student of the
present time.
The various sources from which palæontological and zoological
information has been derived have, for the most part, been adverted to
in the text or in the footnotes. The Editor, however, has especially
to acknowledge the kindness of Mr. J. Morris, F.G.S., in allowing
him to refer to the proof-sheets of the forth-coming edition of his
"Catalogue of British Fossils," and thereby affording him important
assistance in making correct statements of the distribution of the
Fossil Remains of the Crustacea, Insecta, and Vertebrata, in the strata
of the British Islands.
T. Rupert Jones.
PREFACE TO THE FIRST EDITION.
In the first edition of the Wonders of Geology, an intention was
expressed of immediately publishing, as a sequel to those volumes,
"First Lessons," or an Introduction to the Study of Petrifactions, for
persons wholly unacquainted with the nature of Fossil Remains; but the
completion of the contemplated work was unavoidably postponed, from
year to year, by the long and severe indisposition of the Author.
In the meanwhile several works professing the same object have issued
from the press; and an enlarged edition of Sir C. Lyell's "Elements"
has also appeared, in which the elementary principles of physical
Geology are fully illustrated, and numerous figures given of the
characteristic fossils of the several formations, or groups of strata.
But that department of the science which especially treats of Organic
Remains is necessarily considered in a cursory manner; and a work
upon the plan originally contemplated by the Author seems still to be
required, to initiate the young and uninstructed in the study of those
Medals of Creation--those electrotypes of nature--the mineralized
remains of the plants and animals which successively flourished in the
earlier ages of our planet, in periods incalculably remote, and long
antecedent to all human history and tradition.
With this conviction the present volumes are offered, with such
modifications of the original plan as circumstances have rendered
necessary, as a guide for the Student and the Amateur Collector of
fossil remains; for the intelligent Observer who may desire to possess
a general knowledge of the subject, without intending to pursue
Geology as a science; and for the Tourist who may wish, in the course
of his travels, to employ profitably a leisure hour in quest of those
interesting memorials of the ancient physical revolutions of our globe,
which he will find everywhere presented to his observation.
Crescent Lodge, Clapham Common, _May_, 1844.
ADDRESS TO THE READER.
"Some books are to be tasted--others to be swallowed--and some few to
be chewed and digested; that is, some Books are to be read only in
parts--others to be read, but not curiously--and some few to be read
wholly and with diligence and attention."--Lord Bacon's Essays.
Anxious that the "Courteous Reader" should derive from this work all
the information it is designed to impart, the Author presumes to
offer a few words in explanation of the plan upon which it has been
constructed, and some suggestions as to the best means of rendering its
contents most available to the varied tastes and pursuits of different
classes of readers.
In its arrangement, a three-fold object was had in view; namely, in the
first place, to present such an epitome of Palæontology, the science
which treats of the fossil remains of the ancient inhabitants of the
Globe, as shall enable the intelligent Observer to comprehend the
nature of the principal discoveries in modern Geology, and the method
of investigation by which such highly interesting, and unexpected
results, have been obtained..
Secondly, to assist the Collector in his search for Organic
Remains,--directing attention to those objects which possess
the highest interest, and are especially deserving of accurate
examination--instructing him in the art of developing and preserving
the specimens he may discover--and pointing out the means to be
pursued, for ascertaining their nature, and their relation to existing
plants or animals.
Thirdly, to place before the Student a familiar exposition of the
elementary principles of Palæontology, based upon a general knowledge
of the structure of vegetable and animal organization; to excite in his
mind a desire for further information, and prepare him for the perusal
and study of works of a higher order than these unpretending volumes;
and to point out the sources from which the required instruction may be
derived.
Although fully aware of the imperfect manner in which these intentions
are fulfilled, the Author hopes that the indulgence claimed by one of
the most able writers of our times may be extended to him; and that,
"if the design be good upon the whole, the work will not be censured
too severely for those faults, from which, in parts, its very nature
would scarcely allow it to be free."[1]
[1] Sir E. B. Lytton--preface to the second edition of "The Disowned."
With regard to the best means of making use of these volumes, the
advice of the great founder of Inductive Philosophy, on the Study of
Books in general, expressed in the quotation prefixed to this address,
is peculiarly applicable to the different classes of readers for whom
the work is designed.
Thus, "_the Book may be tasted, that is, read only in parts_," by the
intelligent reader, who requires but a general acquaintance with the
subjects it embraces. The perusal of the introductory and concluding
remarks of each chapter, of the general descriptions of fossil
remains, and of the circumstances under which they occur,--omitting the
scientific terms and descriptions,--and a cursory examination of the
illustrations, will probably satisfy his curiosity; and the work may
be transferred to the library for occasional reference, or taken as a
travelling companion and guide to some interesting geological district.
But the Book "_must be swallowed, that is, read, but not curiously_,"
by the reader desirous of forming a collection of organic remains. A
general acquaintance with its contents, and a careful investigation
of the characters of the fossils, and comparison with the figures and
descriptions, will be requisite to enable the amateur collector to
determine the nature of the specimens he may discover.
By the Student the Book "_must be digested, that is, read wholly, and
with diligence and attention_." He should fully comprehend one subject
before he advances to the consideration of another, and should test
the solidity of his knowledge by practical research. He should visit
some of the localities described; collect specimens, and develope
them with his own hands; examine their structure microscopically;
nor rest satisfied until he has determined their general characters,
and ascertained their generic and specific relations. Nor is this an
arduous or irksome task; by a moderate degree of attention, a mind
of average ability may quickly overcome the apparent difficulties,
and will find in the knowledge thus acquired, and in the accession of
mental vigour which such investigations never fail to impart, an ample
reward for any expenditure of time and trouble.
It is, indeed, within the power of every intelligent reader, by
assiduity and perseverance, to attain the high privilege of those who
walk in the midst of wonders, in circumstances where the uninformed and
uninquiring eye can perceive neither novelty nor beauty; and of being
"Even as one,
Who by some secret gift of soul or eye,
In every spot beneath the smiling sun.
_Sees where the Springs of living Waters lie!_"
TABLE OF CONTENTS.
~~~~~~~~
VOL. I.
Dedication, p. v.
Prefatory Note to the Second Edition, vii.
Preface to the First Edition, ix.
Address to the Reader, xi.
Table of Contents, xv.
Description of the Plates, xix.
List of Lignographs in Vol. I., xxxi.
Introduction, 1.
Preliminary Remarks:--On the Plan of the Work and the Arrangement and
Subdivision of the subjects it embraces, 8. Works of Reference, 8.
Explanation of Terms, 11. List of subjects, 12.
PART I.--Stratigraphy of the British Islands, and the Nature of
Fossils, 15.
Chapter I.--On the Nature and Arrangement of the British Strata and
their Fossils, 15.
Chapter II.--Synopsis of the British Strata, 23. Chronological
Arrangement of the British Formations; Modern or Human Epoch;
Post-Pliocene, 23. Tertiary Epochs, 24. Secondary Epochs, 25.
Palæozoic Epochs, 30. Hypogene Rocks, 34. Volcanic Rocks, 35.
Chapter III.--On the Nature of Fossils or Organic Remains, 37.
Incrustations, 38. Silicification, 40. Animal Remains, 43. Hints
for Collecting Fossil Bones, 45.
PART II.--Fossil Botany, 51.
Chapter IV.--Fossil Botany, 51. Fossil Vegetables, 51. On the
investigation of the Fossil Remains of Vegetables, 54. Endogenous
Stems, 56. Exogenous Stems, 56. Structure of Coniferæ, 57.
Botanical principles, 58. Exogens, 59. Endogens, 59. Investigation
of Fossil Stems, 61. Fossil Leaves, 64. On the Microscopical
Examination of Fossil Vegetables, 65. Mode of preparing slices of
Fossil Wood, 66.
Chapter V.--On Peat-wood, Lignite, and Coal, 69. Submerged Forests;
Peat, 70. Lignite, Brown-coal, Cannel-coal, 71. Bovey-coal,
72. Jet, 72. Wealden Coal, 73. Coal, 76. Stratification of a
Coal-field, 80. Origin and Nature of Coal, 82.
Chapter VI.--Fossil Vegetables, 86. Fossil Cryptogamia, 87. Recent
Diatomaceæ, 88. Fossil Diatomaceæ, 93. Fossil Coniferæ, 100. Fossil
Fucoids, 101. Chondrites, 101. Moss-agates and Mocha-stones, 103.
Equisetaceæ, 105. Calamites, 107. Filicites or Fossil Ferns, 109.
Pachypteris, 112. Sphenopteris, 112. Cyclopteris, 114. Neuropteris,
115. Glossopteris, 115. Odontopteris, 116. Anomopteris, 116.
Tœniopteris, 117. Pecopteris, 118. Lonchopteris, 119. Phlebopteris,
120. Clathropteris, 121. Stems of Arborescent Ferns, 122.
Caulopteris, 123. Psarolites, 123. Sigillariæ and Stigmariæ, 125.
Internal Structure of Sigillariæ, 130. Stigmaria, 132. Lepidodendron,
137. Lepidostrobus, 140. Triplosporite, 142. Lycopodites, 143. Halonia
and Knorria, 143. Asterophyllites, 145. Sphenophyllum, 147.
Cardiocarpon, 147. Trigonocarpum, 148. Fossil Cycadaceæ, 150.
Pterophyllum, 152. Zamites, 152. Trunks and Stems of Cycadaceæ, 156.
Mantellia, 157. Clathraria, 159. Endogenites, 163. Fossil Coniferæ,
164. Fossil Coniferous Wood, 167. Palæoxylon, 167. Pence, 168.
Araucarites, 168. Sternbergia, 168. Petrified Forests of
Conifers, 169. Coniferous Wood in Oxford Clay, 172. Coniferous Wood
in Chalk, 173. Tertiary Coniferous Wood, 175. Fossil Foliage and
Fruit of Coniferæ, 175. Araucaria, 175. Pinites, 176. Walchia, 177.
Abietites, 178. Thuites, 180. Voltzia, 180. Taxites, 181. Nœggerathia,
181. Fossil Resins and Amber, 181. Fossil Palms, 183. Fossil
Palm-leaves, 185. Fossil Fruits of Palms, 186. Fossil Fruits from the
Isle of Sheppey, 186. Nipadites, 190. Fossil Fruit of Pandanus, 192.
Wood perforated by Teredines, 193. Fossil Liliaceæ, 194. Fossil
Fresh-water Plants, 195. Fossil Fruits of Chara, 195. Fossil
Nymphaeæ, 197. Fossil Flowers, 197. Fossil Angiosperms, 197. Fossil
Flora of Œningen, 200. Carpolithes, 202. Fossil Dicotyledonous Trees,
203. Dicotyledons of the Cretaceous Epoch, 205. Retrospect of Fossil
Botany, 206. On Collecting British Fossil Vegetables, 211. British
localities of Fossil Vegetables, 213.
PART III.--Fossil Zoology, 216.
Chapter VII.--Fossil Zoophytes; Porifera or Amorphozoa; Polypifera
or Corals; Bryozoa or Molluscan Zoophytes, 218. Fossil Porifera,
219. On the Sponges in Chalk and Flint, 222. Spongites, 223.
Fossil Zoophytes of Faringdon, 226. Scyphia, 227. Cnemidium, 228.
Chenendopora, 228. Tragos, 229. Siphonia, 230. Choanites, 233.
Paramoudra, 236. Clionites, 238. Spicula of Sponges, 238.
Spiniferites, 239. Ventriculites, 242. Polype in Flint, 250. Fossil
Polypifera, 251. Graptolites, 255. Fungia, 256. Anthophyllum, 257.
Turbinolia, 257. Caryophillia, 257. Favosites, 258. Catenipora, 259.
Springopora, 259. Lithostrotion, 260. Cyathophyllum, 260. Astræa,
262. Madrepora, 264. Millepora, 264. Lithodendron, 264. Gorgonia,
265. Fossil Bryozoa, 265. Flustra, 266. Crisia, 269. Retepora,
269. Fenestrella, 270. Petalæpora, 270. Pustulopora, 270.
Homœsolen, 271. Idmonea, 271. Verticillipora, 273. Lunulites, 273.
Geological Distribution of Fossil Zoophytes, 273. On Collecting
Fossil Corals, 276. British localities, 278.
Chapter VIII.--Fossil Stelleridæ; comprising the Crinoidea and
the Asteriadæ, 280. Crinoidea, 281. Pentacrinus, 282. Fossil
Crinoidea, 283. Fossil Stems of Crinoidea, 284. Pulley-stones,
285. Apiocrinus, 288. Bourqueticrinus, 291. Encrinus, 292.
Pentacrinites, 293. Actinocrinus, 295. Cyathocrinus, 295.
Rhodocrinus, 297. Eugeniacrinus, 297. Pentremites, 297. Cystidea,
298. Marsupites, 299. Fossil Asteriadæ, 301. Fossil Ossicula of
Star-Fishes, 303. Ophiura, 304. Goniaster, 306. Asterias, 307.
Geological Distribution of the Crinoidea, 308.
Chapter IX.--Fossil Echinidæ, 311. Cidaritidæ, 314. Cidaris, 316.
Diadema, 318. Echinus, 318. Salenia, 318. Spines of Cidarites,
319. Flint Casts of Cidarites, 320. Cidaritidæ of the Palæozoic
Rocks, 321. Clypeasteridæ, 322. Galerites, 322. Holectypus, 324.
Discoidea, 324. Clypeideæ, 325. Clypeus, 325. Nucleolites, 326.
Spatangidæ, 326. Ananchytes, 327. Micraster, 328. Toxaster, 329.
Holaster, 330. Geological Distribution of Echinites, 330. On
Collecting and Developing Echinodermata, 331.
Chapter X.--Fossil Foraminifera; and Microscopical Examination of
Chalk and Flint, 336. Foraminifera, 339. Classification of the
Foraminifera, 342. Nummulites, 344. Orbitoides, 346. Siderolina,
346. Fusulina, 346. Nodosaria, 347. Cristellaria, 348. Flabellina,
348. Polystomella, 348. Lituola, 348. Spirolina, 349. Globigerina,
350. Nonionina, 350. Rotalia, 351. Rosalina, 351. Textularia,
352. Verneuilina, 352. Strata composed of Foraminifera, 352.
Foraminifera of the Chalk and Flint, 355. Fossil Remains of the
Soft Parts of Foraminifera, 357. Foraminifera-Limestones of
India, 362. Foraminifera-deposit at Charing, 363. Foraminifera of
the Oolite, Lias, &c. 364. Foraminifera-deposits of the United
States, 364. Foraminifera of the Carboniferous Formations, 365.
Foraminifera-Limestone of New Zealand, 366. Tertiary Foraminifera,
366. Foraminifera of the Fens of Lincolnshire and Cambridgeshire,
367. Recent Foraminifera-deposit at Brighton, 368. Geological
Distribution of the Foraminifera, 369. Instructions for the
Microscopical Examination of Chalk, Flint, and other Rocks, 371.
Chapter XI.--Fossil Testaceous Mollusks, or Shells, 374. Mollusca,
374. Acephala, 375. Encephala, 378. Fossil Bivalve Shells, 381.
Shell-Rocks, 382. Fossil Brachiopoda, 388. Terebratula, 389.
Spirifer, 390. Rhynchonella, 391. Pentamerus, 391. Orthis, Leptæna,
and Productus, 392. Calceola, 392. Crania, 392. Orbicula, 392.
Obolus, 392. Lingula, 393. Hippurites, 393. Fossil Shells of the
Lamellibranchiates, 394. Monomyaria, 395. Ostrea, 395. Gryphæa,
396. Spondylus, 398. Plagiostoma, 399. Plicatula, 400. Pecten, 400.
Inoceramus, 401. Avicula, 404. Dimyaria, 404. Venericardia, 405.
Pectunculus, 405. Nucula, 406. Pinna, 406. Mytilus, 407. Modiola,
407. Pholadomya, 408. Pholas, 408. Teredo, 410. Trigonia, 412.
Fossil Fresh-water Bivalves, 413. Unio, 414. Cyclas, 416. Fossil
Pteropoda, 417. Fossil Gasteropoda, 417. Fresh-water Univalves,
421. Paludina, 421. Limnæus, 423. Planorbis, 423. Melanopsis, 424.
Marine Univalves, 424. Fusus, 425. Pleurotoma, 425. Cerithium,
425. Potamides, 425. Rostellaria, 426. Dolium, 426. Trochus,426.
Solarium, 426. Conus, 426. Pleurotomaria, 427. Euomphalus, 429.
Murchisonia, 430. Sphærulites, 430. Molluskite, 432. Geological
Distribution of Bivalve and Univalve Mollusks, 436. On the
Collecting and Arranging Fossil Shells, 441. British Localities of
Fossil Shells, 443.
CONTENTS OF VOL. II.
Description of Frontispiece (Plate II.)
List of Lignographs in Vol. II.
Table of Contents.
PART III.--_continued_.
Chapter XII.--Fossil Cephalopoda, 447.
Chapter XIII.--Fossil Articulata, 503.
Chapter XIV.--Fossil Ichthyology; Sharks, Rays, and other Placoid
Fishes, 562.
Chapter XV.--Fossil Ichthyology; Ganoid, Ctenoid, and Cycloid Fishes,
600.
Chapter XVI.--Fossil Reptiles; Enaliosaurians and Crocodiles, 643.
Chapter XVII.--Fossil Reptiles; Dinosaurians, Lacertians,
Pterodactyles, Turtles, Serpents, and Batrachians, 684.
Chapter XVIII.--Fossil Birds, 759.
Chapter XIX.--Fossil Mammals, 775.
PART IV.--Geological Excursions, 827.
Miscellaneous, 905.
General Index, 909.
DIRECTIONS TO THE BINDER.
Plate I.--Frontispiece to Vol. I.
Plate II. Frontispiece to Vol. II.
Plates III., IV., V., and VI., to follow the Table of Contents, and be
placed opposite the description of each.
Lign. 247, to face page 770.
DESCRIPTION
OF THE
FRONTISPIECE OF VOL. I.
PLATE I.
Fig. 1.--A Fern in Coal-shale, from Leicestershire.
2.--A Crustacean in Limestone, from Solenhofen.
3.--A Fish (_Pycnodus rhombus_) in Limestone; from near
Castel-a-mare.
4.--Half the Lower Jaw of a Hyena, from a fissure in a
sandstone rock, near Maidstone.
5.--An Ammonite, from the Isle of Portland.
DESCRIPTION OF THE VIGNETTE OF VOL. I.
A Group of Fossils, containing
Ammonites Mantellii, from the _Chalk-marl_, Sussex.
Turrilites costatus, from the _Lower Chalk_, Rouen.
Chondrites Bignoriensis, from the _Chalk-marl_, Sussex.
Echinus and Fusus, from _Tertiary strata_, Palermo.
DESCRIPTION OF PLATE II.
_The Frontispiece of Vol. II._
A Fossil Fish of the Salmon tribe, allied to the Smelt; from the Chalk,
near Lewes, in Sussex.
[See Vol. II. pages 626 and 628.]
[Illustration: _Pl. 3._
_J. Dinkel del. G. Scharf lithog._
_Printed by Hullmandel & Walton_]
DESCRIPTION OF PLATE III.
_Incrustations, and Fossil Plants._
Figs. 1, 2, 3.--Twigs of Larch and Hawthorn, coated with tufa, or
travertine, from having been exposed to the dripping of
an incrusting spring; from Russia; see p. 39.
5.--A branch of recent _Chara_, with its fruit, with a thin
pellicle of incrustation. Matlock.
6, 7.--Hazel-nuts, from Belfast Lough: fig. 6 is lined with
crystals of calcareous spar; fig. 7 is filled with a
solid mass of the same mineral; see p. 71.
4, 8.--Impressions of Dicotyledonous Leaves in Gypseous Marlstone,
from Stradella, near Pavia; see p. 201.
9.--Eocene Lacustrine or Fresh-water Limestone, from East Cliff
Bay, Isle of Wight, with stems and seeds of Charge: slightly
magnified; see p. 195.
10.--Encrusted Twigs, from Matlock; the vegetable matter has
perished, and left tubular cavities; see p. 39, and p. 873.
[Illustration: _Pl. 4._
_J. Dinkel del. G. Scharf lithog._
_Printed by Hullmandel & Walton_]
DESCRIPTION OF PLATE IV.
Various species of recent Diatomaceæ, to illustrate the Fossil remains
of this Tribe of Vegetables.
_For detailed descriptions, see pages 87-100._
Figs. 1 to 5.--Various kinds of _Xanthidia_: figs. 2, 3, 4, found in a
pond on Clapham Common, and fig. 1. living in a pond
near Westpoint, United States.
1.--Xanthidium _furcatum_: 1/24 of a line in diameter.
2.-- --------- _hirsutum_: 1/36.
3.-- --------- _aculeatum_: 1/24.
4.-- --------- _fasciculatum_: 1/24.
5.-- -------------------- variety of the above.
2*.--Pyxidicula operculata; Carlsbad, Bohemia: 1/48 of a line in
diameter.
6.--Bacillaria vulgaris. 1/36 of a line in diameter. Pond on
Clapham Common.
7.--Cocconeis scutellum: from the Baltic: 1/24 of a line.
8.--Navicula viridis: 1/6 of a line. Ponds on Clapham Common.
9.--The same; a side view; showing the currents produced in the
water by the animal when in locomotion.
10.--Gallionella lineata: 1/36 of a line. Ponds on Clapham Common.
11.--Gallionella moniliformis: 1/72 of a line.
12.--Synhedra ulna: 1/9 of a line: the point _a_, marks the pedicle
of attachment. Ponds on Clapham and Wandsworth Commons.
13.--Podosphenia gracilis: 1/12 of a line; attached to a thread of
_Calothria_ and having by self-division formed a
radiating cluster. Common in the ditches communicating with
the Thames in Battersea-fields.
14.--Navicula splendida: 1/12 of a line in diameter.
15.--Lateral view of the same.
16.--Eunotia turgida: 1/14 of a line; the empty shell, with
sixty-five ribs, viewed laterally.
17.--A living group of the same: 1/20 of a line: a piece of
_Conferva rivularis_, beset with these animalcules.
The smaller species are _E. Westermanni_.
[All the above organisms were figured and described by Ehrenberg as
animals (_Polygastrica_), and are comprised in his family _Bacillaria_;
they are now, however, regarded as unquestionably vegetable structures,
belonging to the family of Algæ, termed _Diatomaceæ_.]
[Illustration: _Pl. 5._
_J. Dinkel del. G. Scharf lithog._
_Printed by Hullmandel & Walton_]
DESCRIPTION OF PLATE V.
_Illustrative of the Structure of Fossil Vegetables._
Fig. 1.--Polished transverse section of silicified Monocotyledonous Wood,
from Antigua; p. 185.
1_a_.--Magnified 20 times linear.
1_b_.--Magnified 75 times linear.
2_a_.--Transverse section of silicified Coniferous Wood
(_Abies Benstedi_) from the Kentish Rag, near Maidstone
(Iguanodon quarry), × 120 linear; p. 173.
2_b_.--Vertical or longitudinal section of the same, × 250
linear.
3_a_.--Transverse section of calcareous coniferous wood, from
Willingdon, Sussex, × 80 linear; p. 173.
3_b_.--Longitudinal section of the above, × 120 linear.
4.--Slice of a transverse section of a recent Dicotyledonous Stem;
showing, 1st, Pith or medullary column, occupying the centre;
2d, Four bands of woody layers, separated by condensed lines
of elongated tissue in series, and having large regular
openings of vessels, with numerous medullary rays running
continuously from the central pith to the bark; 3d, the bark.
(_From Mr. Witham._)
5.--Slice of a transverse section of a recent gymnospermous
phanerogamic stem (of a Cycas), having a central pith, with
woody layers separated by a condensed line, and consisting of
elongated cellular tissue, arranged in a regular series;
medullary rays and bark. (_From Mr. Witham._)
6.--Bundles of vascular tissue in Stigmaria ficoides, × 12 linear.
See p. 135.
The two strands of vessels that appear as if on the surface (and
are of a looser texture) are part of the vascular tissue of
the stem, and become inflected (that is, bent over), and give
rise to a band of vessels (the darker band seen between the
above), that passes towards the bark or cortical covering.
7.--Portion of a transverse section of one of the bundles of
vascular tissue of _Sigillaria elegans_, × 20 linear.
(From _M. Brongniart._) See p. 131.
The convex portion on the left, and which in the original stem
is situated towards the centre, is composed of the medullary
vascular tissue formed of vessels irregularly disposed.
The longitudinal bundles are the woody fibres arranged in a
radiated circle: the smooth interspaces are medullary rays.
The two distinct roundish spots of vascular tissue on the right
of the ligneous zone occur irregularly on the outside of the
woody circle, and are supposed to be detached bundles of the
ligneous zone extending towards the leaves. See p. 131.
[Illustration: _Pl. 6._
_J. Dinkel del. G. Scharf lithog._
_Printed by Hullmandel & Walton_]
DESCRIPTION OF PLATE VI.
_Illustrative of the Structure of Fossil Teeth._
Fig. 1_a_.--Tooth of _Psammodus porosus_, from the Mountain Limestone.
See p. 587.
1_b_.--Vertical section, a portion × 75 linear.
1_c_.--Transverse section of the same, × 75.
2_a_.--Tooth of _Ptychodus polygurus_, from the Chalk, near
Lewes. See p. 585.
2_b_.--Portion of longitudinal section, × 20.
2_c_.--Portion of transverse section, × 20.
3_b_.--Tooth of the _Labyrinthodon Jægeri_, from the New Red
sandstone near Wirtemberg; half the natural size: the specimen
presented by Dr. Jæger. See p. 742.
3_a_.--A moiety of a transverse polished section, × 20.
3_b_.--Portion of a vertical section near the apex, × 20.
3_c_.--One of the anfractuosities of fig. 3_a_ × ×.
4_a_.--Crown or upper portion of a tooth of a young _Iguanodon_,
from Tilgate Forest. See p. 697.
4_b_.--Portion of a vertical section of the above, × 20.
4_c_.--A small portion of a transverse section of the same, × 20.
5.--Tooth of _Goniopholis_, Tilgate Forest: half the natural size.
See p. 678.
6_a_.--Tooth of a reptile (probably of the _Hylæosaurus_), from
Tilgate Forest; half the natural size. See p. 690.
6_b_.--Portion of a vertical section of the same, × 20.
7_a_.--Tooth of _Megalosaurus_, from Tilgate Forest. See p. 687.
7_b_.--Portion of a vertical section of the same, × 10.
8.--A small portion of a vertical section of a tooth of _Dendrodus_.
See p. 618.
9.--Portion of a transverse section of the base of a tooth of
_Ichthyosaurus_, × 20. See p. 665.
10_a_.--Tooth of _Lepidotus_, Tilgate Forest. See p. 606.
10_b_.--The upper figure is a transverse section, and the lower
a vertical section of the same, × 20.
LIST OF LIGNOGRAPHS IN VOL. I.
============
(_Illustrative of Fossil Botany._)
LIGN. PAGE
1. Sections of Recent Vegetables 55
2. Sections of Fern-Stems 62
3. Nodule of Ironstone, enclosing a Fern Leaf 69
4. Siliceous Frustules of Diatomaceæ, and Spicules of Spongillæ 94
5. Fossil Gallionellæ 96
6. Organic Bodies in Porcelain Earth 97
7. Microphytes from the Tertiary deposits at Richmond, U.S. 98
8. Confervites Woodwardii 101
9. Chondrites Bignoriensis 102
10. Delesserites (Fucoides) Lamourouxii 103
11. Moss and Conferva in transparent quartz 104
12. Equisetum Lyellii 105
13. Equisetites columnaris 106
14. Calamites decoratus 107
15. Calamites in Coal-shale 108
16. Pecopteris Sillimani 110
17. Pachypteris lanceolata 112
18. Sphenopteris elegans 112
19. Sphenopteris nephrocarpa 113
20. Sphenopteris Mantellii 113
21. Cyclopteris trichomanoides 114
22. Neuropteris acuminata 115
23. Glossopteris Phillipsii 116
24. Odontopteris Schlotheimii 116
25. Anomopteris Mougeotii 117
26. Tœniopteris latifolia 118
27. Fig. 1, Pecopteris Murrayana 118
2, Pecopteris lonchitica 118
28. Lonchopteris Mantellii 119
29. Fig. 1, Phlebopteris Phillipsii 120
2, Phlebopteris propinqua 120
30. Clathropteris meniscoides 121
31. Caulopteris macrodiscus 123
32. Base of a Trunk of a Sigillaria, with root 126
33. Sigillariæ, in Coal Shale 128
34. Sigillaria Saullii 129
35. Silicified Stem of Sigillaria elegans 130
36. Stigmaria ficoides 133
37. Transverse section of Stigmaria ficoides 135
38. Erect Stem of a Sigillaria, with Roots 136
39. A Terminal Branch of a Lepidodendron 138
40. Lepidostrobi, the Fruit of Lepidodendra 141
41. Stems of Halonia and Knorria, from the Coal Formation 144
42. Asterophyllites equisetiformis 147
43. Fig. 1, Sphenophyllum Schlotheimii 148
2, Sphenophyllum erosum 148
44. Fossil Fruits, or Seed Vessels 149
45. Foliage and upper part of the Stem of Cycas revoluta (recent) 150
46. Part of a leaf of Pterophyllum comptum 152
47. Part of a leaf of Zamites pectinatus 153
48. Fruit of Zamites Mantellii 154
49. Fossil Fruits of Cycadeous Plants 156
50. Mantellia nidiformis 157
51. Mantellia cylindrica 158
52. Clathraria Lyellii, inner Axis of the Stem of 159
53. Clathraria Lyellii, Stem of 160
54. Clathraria Lyellii, part of Stem of 161
55. Clathraria Lyellii, Petiole of 161
56. Clathraria Lyellii, summit of Stem, with petioles 162
57. Clathraria Lyellii, water-worn Stem of 163
58. Fragment of Coniferous Wood in Flint 174
59. Fig. 1, Part of a Branch of Araucaria peregrina 176
2, Calamites nodosus, with foliage 176
60. Walchia hypnoides 178
61. Abietites Dunkeri 179
62. Thuites Kurrianus 180
63. Nipadites and other Fossil Fruits from the Isle of Sheppey 188
64. Fossil Fruits from the Isle of Sheppey 189
65. Fossil Wood perforated by Teredines 193
66. Fossil Fresh-water Plants 196
67. Fossil Fruits and Flower 198
68. Imprints of Dicotyledonous leaves in Gypseous Marlstone 201
(_lllustrative of Fossil Zoology._)
69. Coral and Spongites 224
70. Fossil Zoophytes 227
71. Fossil Sponge 228
72. Fossil Zoophytes 229
73. Siphoniæ from the Greensand 231
74. Polypothecia dichotoma 232
75. Choanites Königi 234
76. Paramoudra in the Chalk 237
77. A group of Spiniferites in Flint 239
78. Spiniferites Reginaldi 241
79. Spiniferites palmatus 241
80. Flints, the forms of which are derived from Zoophytes 243
81. Ventriculites radiatus 244
82. Portions of Ventriculites 245
83. Ventriculites alcyonoides 248
84. A Coral Polype, in flint 250
85. Graptolites in Wenlock Limestone 255
86. Favosites polymorpha 258
87. Corals from the Dudley Limestone 261
88. Fossil Corals 262
89. Corals from the Chalk and Mountain Limestone 268
90. Stems of Encrinites and Pentacrinites 284
91. Recent Comatula and Fossil Crinoidea 286
92. Fossil Crinoidea 289
93. Apiocrinites 291
94. Actinocrinites and Pentacrinite 294
95. Cyathocrinites planus 296
96. Marsupites Milleri 300
97. Fossil remains of Star-fishes 305
98. Goniaster Mantelli 306
99. Asterias prisca 308
100. Fossil Turban Echinus with its Spines 311
101. Cidarites from the Oolite and Chalk 316
102. Fossil Spines of Cidarites 319
103. Echinital remains in flint 320
104. Echinites from the Chalk 323
105. Holectypus inflatus 324
106. Discoidea castanea 325
107. Micraster cor-anguinum 328
108. Toxaster complanatus 329
109. Foraminifera from the Chalk 342
110. Nummulites, or Nummulina 344
111. Foraminifera from the Chalk 347
112. Spirolinites in flint 349
113. Nonionina Germanica (recent) 350
114. Foraminifera in Chalk and flint 351
115. Chalk-dust, chiefly composed of Foraminifera 355
116. Section of a Rotalia in flint 356
117. Rotalia in flint, with the fossilized body of the animal in
the shell 358
118. Soft Bodies of Foraminifera extracted from the Chalk 359
119. Remains of Foraminifera in chalk and flint 361
120. Fossil Oyster, from the Chalk 374
121. Recent Bivalve Mollusc, showing the several parts of the
shell and the animal 377
122. Turritellæ from Bracklesham 383
123. Shell-Conglomerate 385
124. Shell-Limestone, from the mouth of the Thames 386
125. Terebratula and Rhynchonella 388
126. Terebratula and Spirifer 390
127. Shells and Echinite from the Oolite and Lias 397
128. Spondylus spinosus in Chalk-flint 399
129. Inoceramus Cuvieri of the Chalk 401
130. Flint with fragments of Inoceramus perforated by Clionites 403
131. Unio Valdensis 415
132. Cyclas and Melanopsis 416
133. Fossil Shells of Gasteropoda 418
134. Polished Slab of Purbeck Marble 422
135. Univalves from the Chalk of Touraine 427
136. Univalves from the Mountain Limestone 428
137. Murchisonia bilineata 430
138. Sphærulites from the Chalk 431
139. Coprolites and Molluskite 432
THE
MEDALS OF CREATION.
⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼
INTRODUCTION.
"Geology, in the magnitude and sublimity of the objects of which it
treats, ranks next to Astronomy in the scale of the Sciences."--_Sir J.
F. W. Herschel._
Geology, a term signifying a discourse on the Earth, (from two Greek
words: viz. γἡ, _ge_, the earth; and λὁγος, _logos_, a discourse,) is
the science which treats of the physical structure of the planet on
which we live, and of the nature and causes of the successive changes
which have taken place in the organic and inorganic kingdoms, from
the remotest period to the present time, and is therefore intimately
connected with every department of natural philosophy.
While in common with other scientific pursuits it yields the noblest
and purest pleasures of which the human mind is susceptible, it has
peculiar claims on our attention, since it offers inexhaustible and
varied fields of intellectual research, and its cultivation, beyond
that of any other science, is in a great measure independent of
external circumstances; for it can be followed in whatever condition
of life we maybe placed, and wherever our fortunes may lead us.
The eulogium passed by a distinguished living philosopher on scientific
knowledge in general, is strikingly applicable to geological
investigations. "The highest worldly-prosperity, so far from being
incompatible with them, supplies additional advantages for their
pursuit; they may be alike enjoyed in the intervals of the most
active business, while the calm and dispassionate interest with which
they fill the mind, renders them a most delightful retreat from the
agitations and dissensions of the world, and from the conflict of
passions, prejudices, and interests, in which the man of business finds
himself continually involved."[2]
[2] Sir J. F. W. Herschel, "Discourse on the Study of Natural
Philosophy."
From the present advanced state of geological science, particularly
of that department which it is the more especial object of these
volumes to elucidate, namely Palæontology,[3] or the study of Organic
Remains,--it seems scarcely credible, that but little more than a
century ago it was a matter of serious question with naturalists,
whether the petrified shells imbedded in the rocks and strata were
indeed shells that had been secreted by molluscous animals; or whether
these bodies, together with the teeth, bones, leaves, wood, &c. found
in a fossil state, were not formed by what was then termed the plastic
power of the earth; in like manner as minerals, metals, and crystals.
[3] Palæontology: from παλαιος, _palaios_, ancient--οντα, _onta_,
beings--λὁγος, _logos_, a discourse.
In a "Natural History of England," published towards the end of the
last century, it is gravely observed that at Bethersden in Kent, a
kind of stone is found full of shells, "_which is a proof that shells
and the animals we find in them living, have no necessary connexion_."
Another amusing instance of the ignorance on such subjects which
prevailed at no remote period, occurs in a "History of the County
of Surrey," in which it is stated that in a search for coal near
Guildford the borers broke, and "this was thought by Mr. Peter Lely,
the Astrologer, to have been the work of subterranean spirits, who
wrenched off the augers of the miners, lest their secret haunts should
be invaded."
But in the latter part of the seventeenth century, there were several
eminent men in England who were greatly in advance of the age in
which they lived, and strenuously exerted themselves to discover and
promulgate the true principles of Geology. Among these, Dr. Martin
Lister, physician to Queen Anne, was one of the most distinguished.
This accomplished naturalist, in his great work on shells, which
remains to this day a splendid monument of his labours, and of the
talents and filial affection of his two daughters, by whom all the
plates were engraved, figures and describes many fossil shells as real
animal productions, and carefully compares them with recent species.
He also recognised the distinction of strata by the organic remains
they contain; and to him the honour is due of having first suggested
the construction of geological maps;[4] he was likewise well acquainted
with the position and extent of the Chalk and other strata of the South
of England.[5]
[4] See Notes on the Progress of Geology in England, by W. H. Fitton,
M.D. &c. _Philos. Mag._ vols. i. and ii. for 1832 and 1833.
[5] This celebrated physician and British geologist died in 1712, and
was interred in the old church at Clapham; where a tablet to his memory
is affixed to the outside of the north wall of St. Paul's Chapel.
From the foreign writers, who at an early period had obtained some
correct notions of the structure of our planet, and of the nature of
the revolutions it had undergone, I select the following beautiful
and philosophical illustration of the physical mutations to which the
surface of the earth is perpetually subjected. It is from an Arabic
manuscript of the thirteenth century;[6] the narrative is supposed to
be related by Rhidhz, an allegorical personage.
[6] Quoted by Sir C. Lyell in his "Principles of Geology."
"I passed one day by a very ancient and populous city, and I asked
one of its inhabitants how long it had been founded? 'It is, indeed,
a mighty city,' replied he; 'we know not how long it has existed,
and our ancestors were on this subject as ignorant as ourselves.'
Some centuries afterwards I passed by the same place, but I could
not perceive the slightest vestige of the city; and I demanded of a
peasant, who was gathering herbs upon its former site, how long it
had been destroyed? 'In sooth, a strange question,' replied he, 'the
ground here has never been different from what you now behold it.'
'Was there not,' said I, 'of old a splendid city here?' 'Never,'
answered he, 'so far as we know, and never did our fathers speak to us
of any such.'
"On revisiting the spot, after the lapse of other centuries, I
found the sea in the same place, and on its shores were a party of
fishermen, of whom I asked how long the land had been covered by the
waters? 'Is this a question,' said they, 'for a man like you? this
spot has always been what it is now.'
"I again returned ages afterwards, and the sea had disappeared. I
inquired of a man who stood alone upon the ground, how long ago the
change had taken place, and he gave me the same answer that I had
received before.
"Lastly, on coming back again, after an equal lapse of time, I found
there a flourishing city, more populous and more rich in buildings
than the city I had seen the first time; and when I fain would have
informed myself regarding its origin, the inhabitants answered me,
'Its rise is lost in remote antiquity--we are ignorant how long it
has existed, and our fathers were on this subject no wiser than
ourselves.'"
We may smile at the ignorance of the inhabitants of the fabled cities,
but are we in a condition to give a more satisfactory reply should it
be inquired of us, "What are the physical changes which the country you
inhabit has undergone?"--and yet cautious observation, and patient and
unprejudiced investigation, are alone necessary to enable us to answer
the interrogation.
Dismissing from his mind all preconceived opinions, the student must
be prepared to learn that the earth's surface has been, and still is,
subject to perpetual mutation,--that the sea and land are continually
changing place,--that what is now dry land was once the bottom of the
deep, and that the bed of the present ocean will, in its turn, be
elevated above the water and become land,--that all the solid materials
of the globe have been in a softened, fluid, or gaseous state,--that
the relics of countless myriads of animals and plants are entombed in
the rocks and strata,--and that vast mountain-chains, and extensive
regions, are wholly composed of the petrified remains of beings that
lived and died in periods long antecedent to the creation of the human
race. Astounding as are these propositions, they rest upon evidence
so clear and incontrovertible, that they cannot fail to be admitted
by every intelligent and unprejudiced reader, who will bestow but a
moderate share of attention to the examination of the phenomena, of
which the following pages present a familiar exposition.
I cannot conclude these introductory observations, without adverting
to the incalculable benefits which result from scientific pursuits in
general, and of Geology in particular. An able modern writer has justly
remarked:--"It is fearfully true, that nine-tenths of the immorality
which pervades the better classes of society, originate from the want
of an interesting occupation to fill up the vacant time; and as the
study of the natural sciences is as attractive as it is beneficial, it
must necessarily exert a moral and even religious influence upon the
young and inquiring mind. The youth who is fond of scientific pursuits
will not enter into revelry, for frivolous or vicious excitements will
have no fascination for him. The overflowing cup, the unmeaning or
dishonest game, will not entice him. If any one doubts the beneficial
influence of these studies on the morals and character, I would ask him
to point out the immoral young man who is devotedly attached to any
branch of natural science: I never knew such an one. There may be such
individuals--for religion only can change the heart--but if there be,
they are very rare exceptions; and the loud clamours which are always
raised against the man of science who errs, prove how rarely the study
of the works of the Creator fails to exert an ennobling effect upon a
well-regulated mind. Fortunate, indeed, are the youth of either sex,
who early imbibe a taste for natural knowledge, and whose predilections
are not thwarted by injudicious friends."
And while Geology exerts this hallowing influence on the character, it
possesses the great advantage of presenting subjects adapted to every
capacity; on some of its investigations the highest intellectual powers
and the most profound acquirements in exact science are required; while
many of its problems may be solved by any one who has eyes and will use
them; and innumerable facts illustrative of the ancient condition of
our planet, and of its inhabitants, may be gathered by any diligent and
intelligent observer.
But it is surely unnecessary to dwell on the interest and importance
of a study, which instructs us that every pebble we tread upon bears
the impress of the Almighty's hand, and affords evidence of Creative
wisdom; that every grain of sand, every particle of dust scattered
by the wind, may be composed of the aggregated skeletons of beings,
so minute as to elude our unassisted vision, but which possessed an
organization as marvellous as our own;--a science whose discoveries
have realized the wildest imaginings of the poet,--whose realities
far surpass in grandeur and sublimity the most imposing fictions
of romance;--a science, whose empire is the earth, the ocean, the
atmosphere, the heavens;--whose speculations embrace all elements,
all space, all time;--objects the most minute, objects the most
colossal;--carrying its researches into the smallest atom which
the microscope can render accessible to our visual organs,--and
comprehending all the phenomena in the boundless Universe, which the
powers of the telescope can reveal.
And as no branch of natural philosophy can more strongly impress
the mind with that deep sense of humility and dependence, which
the contemplation of the works of the Eternal is calculated to
inspire, so none can more powerfully encourage our aspirations after
truth and wisdom. Every walk we take offers subjects for profound
meditation,--every pebble that attracts our notice, matter for serious
reflection; and contemplating the incessant dissolution and renovation
which are taking place around us in the organic and inorganic kingdoms
of nature, we are struck with the force and beauty of the exclamation
of the poet--
My heart is awed within me, when I think
Of the great miracle which still goes on
In silence round me--the perpetual work
Of Thy Creation, finished, yet renewed
For ever!
PRELIMINARY REMARKS.
ON THE PLAN OF THE WORK, AND THE ARRANGEMENT AND SUBDIVISION OF THE
SUBJECTS IT EMBRACES.
With the view of economizing space, I would refer the reader to the
following volumes for figures and descriptions of such fossils as are
illustrated therein: by this arrangement I hope to afford the student a
comprehensive view of Palæontology, and yet restrict this work within
the limits which as a manual it would be inconvenient to exceed; at the
same time it will be complete in itself, and afford all the information
required by the amateur collector and general reader.
I. Dr. Buckland's _Bridgewater Treatise_: 2 vols. 8vo.--These volumes
contain numerous excellent figures of organic remains; and as the work
is, or ought to be, found in every good public or private library in
the kingdom, it will be accessible to most of my readers.
II. _The Wonders of Geology, or a Familiar Exposition of Geological
Phenomena_; _sixth_ edition, in two vols, with coloured plates, and
numerous figures; by the Author. Price 18_s._--This work is designed
to afford a general view of Geological phenomena, divested as much as
possible of scientific language: it is illustrated by numerous figures
of organic remains.
III. _Geological Excursions round the Isle of Wight and along the
adjacent Coasts of Hampshire and Dorsetshire._ One volume, richly
illustrated. By the Author. Price 12_s._
IV. _Petrifactions and their Teachings; or a Hand-book to the Gallery
of Organic Remains in the British Museum._ One vol. with many original
figures of the most interesting objects. By the Author.[7] Price 5_s._
[7] The three works above named consist of four volumes uniform with
the present edition of the "Medals of Creation:" this series of six
volumes comprises the popular geological works of the Author.
V. _A Pictorial Atlas of Fossil Remains;_ consisting of Coloured
Illustrations selected from "Parkinson's Organic Remains of a Former
World," and Artis' "Antediluvian Phytology." 1 vol. 4to. with
seventy-four coloured plates, and several lignographs, containing
nearly 900 figures of fossils. By the Author. Price 2_l._ 2_s._
To the above may be added Dana's _Mineralogy_, which treats of the
various mineral substances that enter into the composition of the rocks
and strata in which the fossil remains are imbedded.
A good geological map of Great Britain is indispensable. The small
map published by the Society for the Diffusion of Useful Knowledge,
edited by Sir R. Murchison, price 5_s._, is an excellent compendium;
but Mr. Knipe's large "_Geological Map of the British Isles_" is the
most complete and convenient for the traveller: price 3_l._ 3_s._ By
reference to the map, the geological structure, and the prevailing
fossils of a district, may be ascertained.
The above works are referred to as follows: viz.
_Bd._ Dr. Buckland's Treatise.
_Wond._ The Wonders of Geology.
_Geol. I. of W._ Geology of the Isle of Wight.
_Petrifactions._ Petrifactions and their Teachings.
_Pict. Atlas._ Pictorial Atlas of Organic Remains.
The following works, to which reference will often be made, are thus
denoted:--
_Foss. Flor._ The Fossil Flora of Great Britain, by Dr. Lindley, and
W. Hutton, Esq. 3 vols. 8vo.
_Vég. Foss._ Histoire des Végétans: Fossiles, par M. Adolphe
Brongniart. 1 vol. 4 to.
_Geol. Trans._ Transactions of the Geological Society of London. 5
vols. 4to.; and New Series, in 5 vols.
_Geol. Proc._ Geological Proceedings.
_---- Journ._ ---------- Quarterly Journal.
_Sil. Syst._ The Silurian System, by Sir R. I. Murchison. 2 vols.
4to. with plates and map.
_Org. Rem._ Parkinson's Organic Remains of a Former World. 3 vols.
4to.
_Oss. Foss._ Ossemens Fossiles, par Baron Cuvier. 5 vols. 4to.
5^{me.} edit.
_Min. Conch._ Sowerby's Mineral Conchology. 6 vols. 8vo.
_Odont._ Odontography; a Treatise on the Comparative Anatomy of the
Teeth, by Professor Owen. 2 vols. 8vo.
_Brit. Mam._ British Fossil Mammalia; by the same Author. 1 vol. 8vo.
_Brit. Rep._ Reports on British Fossil Reptiles in the British
Association Transactions for 1839, and 1841; by the same Author.
_Phil. York._ Geology of Yorkshire, by Professor John Phillips. 2
vols. 4to.
_South. D._ Fossils of the South Downs, 1 vol. 4to. 42 plates by the
Author. 1822.
_Geol. S. E._ Geology of the South-east of England. 1 vol. 8vo. by
the same.
_Tilg. For._ Fossils of Tilgate Forest. 1 vol. 4to. 20 plates; by the
same. 1827.
_Poiss. Foss._ Recherches sur les Poissons Fossiles, par M. Agassiz.
4 vols. 4to, and 2 vols, folio.
_Man. Geol._ Manual or Elements of Geology, by Sir C. Lyell. 1 vol.
8vo. Edit. 1852.
The following abbreviations are also employed:--
§ 1. _Relative to the Rocks or Strata._
_Drift._ Alluvial deposits, or Drift.
_Tert._ Tertiary. _Lond. C._ London clay.
_Cret._ Cretaceous formation. _U. Ch._ Upper chalk. _L. Ch._ Lower
chalk.
_Trias._ New Red Sandstone, or Triassic deposits.
_Carb._ Carboniferous or Coal formation.
_Mt. L._ Mountain or Carboniferous limestone.
_Devon._ Devonian or Old Red Sandstone formation.
_Sil. Syst._ Silurian System, or formation.
§ 2. _Relative to Organic Remains._
_nat._ Natural size.
× Magnified in diameter: _e.g._ × 8, magnified eight diameters, &c.
× × Highly magnified; the degree not accurately determined.
_inv._ Invisible to the naked eye.
-- Less than natural: _e.g._ --2/3, reduced to two-thirds the
diameter of the original.
_Lign._ Lignograph or woodcut.
_Explanation of Terms._--Upon the occurrence of a scientific word
apparently requiring explanation, the _meaning_, where practicable,
is for the most part given in a parenthesis; for example, Caulopteris
(_fern-stem_); Phascotherium (_pouch-animal_); carboniferous
(_coal-bearing_); except in the case of arbitrary names, and of those
whose derivation cannot be concisely expressed.[8] With the view of
rendering these volumes more generally useful, English terminology
is in many instances made use of, though involving inelegance of
expression.
[8] Upwards of 300 scientific terms are explained in the Glossary,
"Wonders," vol. ii. p. 915-921.
The work is divided into four parts: the first is an _Introduction to
the Study of Organic Remains_; the second treats of _Fossil Botany_;
the third embraces _Fossil Zoology_; and the fourth, under the head
of _Geological Excursions_, illustrates the principles enunciated in
the course of the work, by practical observations on a few instructive
British localities.
PART I.
1. On the British Strata and their Fossils.
2. Arrangement and Characters of the British Formations.
3. On the Nature of Fossils or Organic Remains.
4. On Mineralized Vegetable Remains, and the mode of
conducting their investigation.
5. On Peat, Lignite, and Coal.
PART II.
FOSSIL BOTANY.
Classification of Fossil Vegetables.
1. On the Fossil Remains of Cryptogamiæ.
2. " " Diatomaceæ.
3. " " Ferns.
4. " " Sigillariæ.
5. " " Lepidodendra.
6. " " Cycadaceæ.
7. " " Coniferæ.
8. " " Palms.
9. " " Angiosperms.
Retrospect.
British Localities of Fossil Plants.
PART III.
FOSSIL ZOOLOGY.
On the Fossil Remains of the Animal Kingdom.
1. Zoophytes; Amorphozoa.
2. " Polypifera.
3. Echinoderms; comprising the
a. Crinoidea, or Lily-shaped animals.
b. Asteriada, or Star-Fishes.
c. Echinida, or Sea-Urchins.
4. Foraminifera.
5. Shell-bearing Mollusca.
6. Articulated animals; comprising
a. Crustaceans.
b. Insects.
7. Fishes.
8. Reptiles.
9. Birds.
10. Mammalia.
11. Man.
Retrospect.
PART IV.
I. Geological Excursions in various parts of England,
illustrative of the method of observing geological
phenomena, and of collecting Fossil Remains.
II. Miscellaneous.
On the prices of Fossils; lists of Dealers, &c.
II. Appendix.
PART I.
⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼
CHAPTER I.
ON THE NATURE AND ARRANGEMENT OF THE BRITISH STRATA, AND THEIR FOSSILS.
"To discover order and intelligence in scenes of apparent wildness and
confusion is the pleasing task of the geological inquirer."--Dr. Paris.
The solid materials of which the earth is composed, from the surface to
the greatest depths within the reach of human observation, consist of
minerals and fossils.
Minerals are inorganic substances formed by natural operations, and are
the product of chemical or electro-chemical action.
Fossils are the durable remains of animals and vegetables which have
been imbedded in the strata by natural causes in remote periods, and
subsequently more or less altered in structure and composition by
mechanical and chemical agencies.
The soft and delicate parts of animal and vegetable organisms rapidly
decompose after death; but the firmer and denser structures, such as
the bones and teeth of the former, and the woody fibre of the latter,
possess considerable durability, and under certain conditions will
resist decay for many years, or even centuries; and when deeply
imbedded in the earth, protected from atmospheric influences, and
subjected to the conservative effects of various mineral solutions,
the most perishable tissues often resist decomposition, and becoming
transformed into stone, may endure for incalculable periods of time.
The calcareous and siliceous cases or frustules of numerous microscopic
plants are so indestructible, and occur in such inconceivable
quantities, that the belief of some eminent naturalists of the last
century, that every grain of flint and lime in certain rocks, may have
been elaborated by the energies of vitality, can no longer be regarded
as an extravagant hypothesis. Some idea may be formed of the large
proportion of the solid materials of the globe that has unquestionably
originated from this source, by a reference to the list of strata
which are wholly, or in great part, composed of animal and vegetable
structures, given in the "Wonders of Geology," p. 888.
There are also immense tracts of country that consist in a great
measure of the remains of plants in the state of anthracite, coal,
lignite, &c.; and districts covered with peat-bogs and subterranean
forests.
Although these relics of animal and vegetable organisms are found in
almost every sedimentary deposit, yet they occur far more abundantly,
and in a better state of preservation, in some strata than in others:
nor are they equally distributed throughout the same bed, but are
heaped together in particular localities, and occur but sparingly,
or are altogether absent, in other layers of the same rock. Neither
are the remains of the same kinds of animals and plants found
indiscriminately in strata of different ages: on the contrary, many
species are restricted to the most ancient, others to the most recent
formations; while some genera range through the entire series of
deposits, and also appear as denizens of the existing seas. Hence
organic remains acquire a high degree of importance, not only from
the intrinsic interest they possess as objects of natural history, but
also for the light they shed on the physical condition of our planet in
the remotest ages, and for the data they afford as to the successive
physical revolutions which the surface of the earth has undergone.
Fossils have been eloquently and appropriately termed Medals
of Creation; for as an accomplished numismatist, even when the
inscription of an ancient and unknown coin is illegible, can from the
half-obliterated effigy, and from the style of art, determine with
precision the people by whom, and the period when, it was struck;
in like manner the geologist can decipher these natural memorials,
interpret the hieroglyphics with which they are inscribed, and from
apparently the most insignificant relics, trace the history of beings
of whom no other records are extant, and ascertain the forms and habits
of unknown types of organization whose races were swept from the face
of the earth, ere the creation of man and the creatures which are his
contemporaries. Well might the illustrious Bergman exclaim, "_Sunt
instar nummorum memorialium, quæ de præteritis globi nostri fatis
testantur, ubi omnia silent monumenta historica_."
To derive from these Medals of Creation all the information they are
capable of affording, regard therefore must be had not only to their
peculiar characters, but also to the geological relations of the
strata in which they are imbedded. Data may be thus obtained by which
the relative age of a formation or group of strata can be determined,
as well as the mode of deposition, and the agency by which it was
effected; whether in the bed of an ocean, or of a lake, or estuary,--by
the action of the sea, or of rivers, or running streams,--by the
effects of icebergs or glaciers,--by slow processes through long
periods of time, or by sudden inundations or deluges,--or by the agency
of volcanoes and earthquakes.
The discovery that particular fossils are confined to certain deposits,
was soon productive of important results, which greatly tended to the
advancement of modern Geology; for although Dr. Lister, more than a
century before, had obtained a glimpse of this law, its principles
were neither understood nor regarded in this country until the late
Dr. William Smith, by his own unaided exertions, proved by numerous
observations on the British strata, its value and applicability for the
identification of a deposit, in districts remote from each other.
This phenomenon did not escape the notice of the distinguished French
philosophers, MM. Cuvier and Brongniart, who in their admirable work,
"_Géographie Minéralogique des Environs de Paris_," enunciated the same
principle:--
"Le moyen que nous avons employé pour reconnoitre au milieu d'un si
grand nombre de lits calcaires, un lit déjà, observé, dans un canton
très-éloigné, est pris de la nature des fossiles renfermés dans chaque
couche; ces fossiles sont toujours généralement les mêmes dans les
couches correspondantes, et présentent d'un système de couche à un
autre système, des différences d'espèces assez notables. C'est un
signe de reconnoissance qui jusqu'à présent ne nous a pas trompés."[9]
[9] Géog. Min. Oss. Foss. tom. ii. p. 266.
Now, though recent discoveries have shown that this rule has many
exceptions, and that its too stringent adoption has been productive of
some erroneous generalizations, yet if employed with due caution it
is fraught with the most interesting results, and is the only certain
basis of our knowledge respecting the appearance, continuance, and
extinction, of the lost races of animals and plants, which were once
denizens of our planet.
[Sidenote: ROCKS AND STRATA.]
In the "Wonders of Geology" will be found a comprehensive sketch of
the composition and arrangement of the several formations or groups
of strata; and a reference to that work will afford the student the
necessary information on this branch of Geology. For the convenience
of the general reader I subjoin a synoptical view of the characters and
relations of the British fossiliferous deposits.
The total thickness of the entire series of rocks within the scope
of human examination, is estimated at from fifteen to twenty miles,
reckoning from the summits of the highest mountains to the greatest
depths hitherto penetrated; and as this vertical section scarcely
amounts to 1/400th of the diameter of the globe, it is familiarly
termed the Earth's crust. The substances of which the sedimentary
strata are composed have been deposited by the action of water, and
subsequently more or less modified in structure and composition by
heat, and by electro-chemical forces. The superficial accumulations of
water-worn detritus, consisting of gravel, boulders, sand, clay, &c.
are termed _Drift_, or _Alluvial_ deposits. When the successive layers
in which the sediments subsided are obvious, the deposits are said to
be _stratified_; when the nature of the materials has been altered by
igneous action or high temperature, but the lines of stratification
are not wholly effaced, the rocks are denominated _metamorphic_
(_transformed_). When all traces of organic remains and of sedimentary
deposition are lost, and the mass is crystalline, and composed of
known products of igneous action, such rocks are named _plutonic_, as
granite, sienite, trap, basalt, porphyry, and the like. Lastly, rocks
resembling the lavas, scoria, and other substances emitted by burning
mountains still in activity, are called _volcanic_.
The sedimentary origin ascribed to ancient crystalline rocks is, of
course, hypothetical, since all evidence of aqueous deposition is
wanting, and the minerals (_mica_, _quartz_, and _felspar_) of which
they are so largely constituted, are not readily soluble in water
under ordinary circumstances. But rocks unquestionably deposited by
water, when exposed to intense heat under great pressure, acquire
a crystalline structure (_Wond._ p. 864); and a series of changes,
from a loose earthy deposit, to compact volcanic lava, may be traced
in numerous instances, so as to leave but little doubt that the
rocks called primitive or primary, _may_ have originally been either
argillaceous, siliceous, or calcareous strata, abounding in organic
remains (_Wond._ p. 873). These crystalline masses have been formed
at successive periods; for granite is found of all ages, occurring
in the most ancient, as well as in comparatively modern epochs. The
difference between the composition and aspect of these rocks, and those
of recent volcanoes, is with much probability ascribed to the fact
that the latter are of sub-aerial origin; that is, were erupted on the
surface, and the gaseous products in consequence escaped; while the
former were ejected at great depths, either beneath the sea, or under
immense accumulations of other deposits, and being thus subjected to
great pressure, the volatile elements were confined, and formed new
combinations: in like manner as chalk when burnt in the open air is
converted into lime, the carbonic acid gas escaping; but when exposed
to the same degree of heat in a closed iron tube, is transformed into
granular marble (_Wond._ p. 104).
From these ancient crystalline rocks generally underlying the
sedimentary deposits, and never appearing as if they had been ejected
from a crater, the term _hypogene_[10] (_nether-formed_) is employed
by Sir C. Lyell to designate the whole class; and they are subdivided
into, 1. _plutonic_, those in which all traces of sedimentary origin
are lost, as granite; and 2. _metamorphic_, those which still manifest
traces of stratification, as mica-schist, &c.
[10] Nether-formed, from ιπο, _hypo_, under; and γἱνομαι, ginomai, to be
formed.
The fossiliferous rocks are, for the convenience of study, separated
into three grand divisions.
1. The Tertiary; comprising the deposits between the Chalk and the
superficial Drift and modern Alluvium.
2. The Secondary; from the _Chalk_ to the _Trias or New Red_, inclusive.
3. The Palæozoic; from the _Permian_ to the _Silurian_; including the
vast series of unfossiliferous slate rocks termed the _Cambrian_, in
which all traces of organic remains are lost.
In the following arrangement the strata are enumerated as if lying
in regular sequence, one beneath the other; but in nature such an
unbroken series has never been observed. A few groups only occur in
a serial order, and these but rarely in their original position. The
beds are for the most part disrupted, and lie in various angles of
inclination; sometimes they are completely retroverted, the newer
strata underlying those upon which they were originally deposited. The
order of succession has been ascertained by careful observation of
the relative superposition of the respective members of the series in
different countries; and from an immense number of facts collected by
able observers in every part of the globe.
This synopsis presents a chronological arrangement of the rocks
according to the present state of geological knowledge, but it must
not be supposed that these rigid distinctions, these hard lines, which
are necessary to facilitate the acquisition of a general idea of the
phenomena attempted to be explained, exist in nature. By whatever
names we designate geological periods, there appear to be no clearly
defined boundaries between them in reference to the whole earth:
such well marked lines may be seen in particular localities, but
daily experience teaches us that there is a blending, and a gradual
and insensible passage, from the lowest to the highest sedimentary
strata, particularly in respect of fossil remains. The terms employed
to designate formations can only be considered as expressing the
predominance of certain characters, to be used provisionally, as a
convenient mode of classifying and generalizing the facts collected,
whilst that knowledge is accumulating which in after times will reveal
the nature and order of succession of the principal events in the
earth's physical history.[11]
[11] "Wonders of Geology," p. 892.
Dr. Buckland's "Bridgewater Treatise" (Vol. II. _frontispiece_)
contains a comprehensive Diagram of the rocks and strata of which the
crust of the earth is composed; it was drawn by the late Mr. Thomas
Webster.
CHAPTER II.
SYNOPSIS OF THE BRITISH STRATA.
"Hard lines are admissible in Science, whose object is not to imitate
Nature, but to interpret her works."--Greenough.
The classification of the stratified rocks is based on three principal
characters; namely, 1, the mineral structure; 2, the order of
superposition; and 3, the nature of the organic remains; the following
synopsis has been drawn up in accordance with these principles.[12]
[12] See "Wonders of Geology," vol. i. pp. 200-207, for a Synoptical
Table of the principal rocks.
CHRONOLOGICAL ARRANGEMENT OF THE BRITISH FORMATIONS.
COMMENCING WITH THE UPPERMOST OR NEWEST DEPOSITS.
Modern or Human Epoch.
Alluvial Deposits: remains of Man and existing species of mammalia.
Post-Pliocene.
Drift; Boulder clay; Till; &c. comprising the superficial irregular
accumulations of transported materials, consisting of gravel, boulders,
sand, clay, &c.
_Observations_.--These beds have been formed by a variety of causes;
by land-floods and inundations, by irruptions of the sea, and by the
agency of glaciers and icebergs. They are the catacombs of the extinct
colossal mammalia--of the mastodon, mammoth, rhinoceros, hippopotamus,
elk, horse, ox, whale, &c. They cannot be definitively separated from
those of the Modern or Human epoch, for the gravel beds near Geneva,
which closely resemble the newest tertiary drift in materials and
position, abound in bones of animals, almost all of which belong to
existing species.[13]
[13] See M. Pictet's "_Palæontologie_."
Tertiary Epochs.
An extensive series, comprising many isolated groups of marine
and lacustrine deposits, containing fossil remains of animals and
vegetables of all classes; the greater number of genera and species in
the most ancient or lowermost beds belong to extinct types.
_Subdivisions_:--
1. The Pliocene[14] (_more new_, or _recent_.[15] _Wond._ p. 221);
strata in which the shells are for the most part of recent
species, having only about ten per cent of extinct forms.
(_Norwich Crag._)
2. The Miocene (_less recent_,[16] _Wond._ p. 221); containing about
20 per cent of recent species of shells. (_Suffolk Crag._)
3. The Eocene (_dawn of recent_,[17] in allusion to the first
appearance of recent species--_Wond._ p. 226); the most ancient
tertiary strata contain but very few existing species of shells;
not more than five per cent. (_London, Hants, and Paris basins._)
[14] In the present state of our knowledge, this arrangement is of great
utility, but it will probably require considerable modification, and
must, perhaps, hereafter be abandoned; for it cannot be doubted, that
strata in which no recent species have yet been found, may yield them
to more accurate and extended observations, and those in which only a
few recent species are associated with a large number of extinct forms,
may have these proportions reversed.
[15] From πλειων, _pleion_, more; and καινος, _kainos_, recent.
[16] From μεἱων, _meion_, less, and recent.
[17] From ἠως, _eos_, the dawn or commencement, and _recent_.
_Obs._--The marine are often associated with fresh-water deposits,
and the general characters of the Tertiary system are alternations of
marine and lacustrine strata. In England the most important Tertiary
deposits are those of the London basin, the Isle of Sheppey, the
south-western coasts of Sussex and Hampshire, the north of the Isle of
Wight, and the eastern coasts of Essex, Norfolk, Suffolk. (_Wond._ p.
226.)
Secondary Epochs.
The Cretaceous or Chalk Formation. (_Wond._ p. 296). A marine
formation, comprising a vast series of beds of limestone, sandstone,
marl, and clay, &c.; characterized by remains of extinct zoophytes,
mollusks, cephalopods, echinoderms, crustaceans, fishes, &c.;
lacertians, crocodilians, chelonians, and other extinct reptiles;
drifted coniferous and dicotyledonous wood and foliage, fuci, &c.
_Subdivisions_:--
1. The _Maestricht beds_. Friable coralline and shelly limestones,
with flints and chert.
2. _Upper Chalk_, with flints } _Craie blanche_ of the French
} geologists.
3. _Lower Chalk_, without flints }
4. _Chalk-marl_ _Craie tufeau._
5. _Firestone_, Malm-rock, Upper } _Glauconie crayeuse._
Greensand, or Glauconite }
6. _Galt_, or Folkstone-marl _Glauconie sableuse._
7. _Shanklin_, or Lower Greensand. { _Formation néocomien_; which
{ is divided into _N. supérieur_,
{ the English upper divisions
{ of the Greensand or Kentish
{ rag; and _N. inférieur_, the
{ lower beds of sand and clay,
{ of the southern shore of the
{ Isle of Wight, at Atherfield.[18]
[18] Another subdivision, with _other_ names (chiefly derived from
French localities), has lately been proposed by M. D'Orbigny; which I
notice with the more regret, since this eminent naturalist formerly
repudiated the censurable practice of many modern systematists,
of changing established names of strata and fossils, without any
just cause. The British geologist will smile to see the Wealden
Formation--so eminently distinguished in England and Germany by its
extent, thickness, and remarkable fauna and flora,--ranked as a
subordinate member of the "_Formation néocomien_," of France.
_Obs._--The Maestricht beds are chiefly composed of fawn-coloured
limestones of friable texture; containing peculiar species of corals,
shells, fishes, reptiles, &c. The _Chalk_ is generally white, but
in some localities is of a deep red, in others of a yellow colour;
nodules, layers, and veins of flint occur in the upper, but are seldom
present in the lower chalk. The _Marl_ is an argillaceous limestone,
which generally prevails beneath the white chalk; it sometimes
contains a large intermixture of green or chlorite sand, and then
is called _Firestone_, or _Glauconite_. The _Galt_ is a stiff, blue
or blackish clay, abounding in shells which frequently retain their
pearly lustre. The _Greensand_ is a triple alternation of sands and
sandstones with clays; and beds of cherty limestone called _Kentish
Rag_.
The Wealden; a formation, whose fluviatile character was first
observed and established by the researches of the author (_Wond._
p. 360). A series of clays, sands, sandstones and limestones, with
layers of lignite, and extensive coal-fields; characterized by the
remains of several peculiar terrestrial reptiles, namely, _Iguanodon_,
_Hylæosaurus_, _Pelorosaurus_, _Megalosaurus_; _Crocodilians_ and
_Chelonians_; _Enaliosaurians_; _Pterodactyles_, &c.; Fishes of
fluviatile and marine genera; Insects of several orders; fresh-water
mollusks and crustaceans; conifers, cycads, ferns, &c.
_Subdivisions_:--
1. _Weald-clay_, with Sussex or Petworth marbles.
2. _Tilgate-grit_, and _Hastings sands_.
3. _Ashburnham clays_, shales, and grey limestones.
4. _Purbeck beds_; argillaceous and calcareous shales, and
fresh-water limestones and marbles. Petrified forest, and layers
of vegetable earth; with Cycads and Conifers.
_Obs._--Clays and limestones, almost wholly composed of fresh-water
snail-shells, and minute crustaceans, generally occupy the uppermost
place in the series in Sussex; sands and sandstones, with shales, and
lignite, prevail in the middle; while in the lowermost, argillaceous
beds, with shelly marbles or limestones, again appear; and, buried
beneath the whole, is a petrified pine-forest, with the trees still
erect, and the vegetable mould undisturbed! The upper clay beds and
marbles form the deep valleys or Wealds of Kent and Sussex, and the
middle series constitutes the Forest-Ridge. The Purbeck strata are
obscurely seen in some of the deepest valleys of eastern Sussex;
they emerge on the Dorsetshire coast, form the Island or Peninsula
whose name they bear, and surmount the northern brow of the Isle of
Portland. On the southern coast of the Isle of Wight, the Wealden
beds emerge from beneath the Greensand strata between Atherfield and
Compton Bay on the western limit, and in Sandown Bay on the eastern;
and their characteristic fossils are continually being washed up on
the sea-shore.
The Jurassic or Oolitic Formation. (_Wond._ pp. 202, and 491). A
marine formation of great extent and thickness, consisting of strata
of limestone and clay, which abound in extinct species and genera of
marine shells, Corals, Insects, Fishes, and terrestrial and marine
Reptiles. Land plants of many peculiar types, and the remains of two
genera of Mammalia.
_Subdivisions_:--
Upper Oolite of Portland, Wilts, Bucks, Berks, &c.
1. _Portland Oolite._ Limestone of an oolitic structure, abounding
in ammonites, trigoniæ, &c. and other marine exuviæ. Green and
ferruginous sands--layers of chert.
2. _Kimmeridge clay._ Blue clay, with septaria, and bands of sandy
concretions--marine shells and other organic remains--_ostrea
deltoidea_. Beds of lignite.
Middle Oolite of Oxford, Bucks, Yorkshire, &c.
1. _Coral oolite_, or Coral rag. Limestone composed of corals, with
shells and echinites.
2. _Oxford clay_; with septaria and numerous fossils. Beds of
calcareous grit, called _Kelloway-rock_ swarming with organic
remains.
Lower Oolite of Gloucestershire, Oxfordshire, and Northamptonshire.
1. _Cornbrash_--a coarse shelly limestone.
2. _Forest marble_; concretions of fissile arenaceous
limestone--coarse shelly oolite--sand, grit, and blue clay.
3. _Great oolite_--calcareous oolitic limestone and freestone;
reptiles, corals, &c., upper beds full of shells.
_Stonesfield slate_;--terrestrial plants, insects, reptiles,
_Mammalia_.
4. _Fullers earth beds_;--marls and clays, with fuller's
earth--sandy limestones and shells.
5. _Inferior oolite_--coarse limestone--conglomerated masses
of terebratulæ and other shells--ferruginous sand, and
concretionary blocks of sandy limestone, and shells.
Lower Oolite, of Brora in Scotland.
1. _Shelly Limestones_--alternation of sandstones, shales, and
ironstone; land-plants.
2. _Ferruginous limestone_, with carbonized wood and shells.
3. _Sandstone and shale; with two beds of coal._
Lower Oolite of the Yorkshire coast.
1. _Cornbrash_--a provincial term for a bluish grey rubbly
limestone, with intervening layers of clay.
2. _Sandstones and clays_, with land-plants, thin beds of coal and
shale--calcareous sandstone and shelly limestone.
3. _Sandstone_--often carbonaceous, with clays; coal-beds, and
ironstone, with remains of vegetables.
4. Limestone; ferruginous and concretionary sands.
_Obs._--The difference observable between the lower beds of the Oolite
in the midland counties, and those of Yorkshire and Scotland, is a
fact of considerable interest. The fluvio-marine accumulations of
vegetable matter in the state of coal, with the remains of land-plants
at Scarborough and Brora, together with the presence of insects,
fresh-water crustaceans, mammalia, and terrestrial plants, in the
Stonesfield slate, attest the existence of neighbouring land, and the
action of rivers and currents.
The Lias. (_Wond._ p. 521) A series of clays, shales, and limestones,
with marine shells, cephalopoda, crinoidea, and fishes in
great abundance; reptiles, (particularly of two extinct genera,
_Plesiosaurus_, and _Ichthyosaurus_,) in immense numbers. Drifted wood
and land plants: coniferæ, cycadesæ &c.
_Subdivisions_:--
1. Upper Lias shale, full of saurian remains, belemnites,
ammonites, &c. intercalated with the lowermost beds of the
Oolite: nodules and beds of limestone.
2. Lias marlstone; calcareous, sandy, and ferruginous strata, very
rich in terebratulæ and other marine shells.
3. Lower Lias clay and shale, abounding in _gryphea incurva_, and
other marine shells; intercalations of sands and clays, with
nodules of limestone.
4. Lias rock; a series of laminated limestones, with clay partings.
Bone-bed, with numerous remains of fishes.
_Obs._--The Lias is the grand depository of those tribes of marine
reptiles, the _Ichthyosauri_ and _Plesiosauri_, whose remarkable
forms, structure, and state of preservation, have excited the
attention even of the most incurious. The collection of these
remains in the British Museum, principally formed by Mr. Hawkins, is
unrivalled.[19]
[19] See "Petrifactions," p. 337-367.
The Trias; or New Red Sandstone Formation,[20] (_Wond._ p. 533).
This group of rocks consists of variegated marls, sandstones, and
conglomerates, frequently of a red colour, with marine shells,
crinoideans, fishes, and reptiles; marine and terrestrial plants. This
series contains extensive deposits of rock-salt, and brine-springs.
[20] Called by some geologists _Poikilitic_ (variegated) group.
This formation comprises the _Trias_, or triple group, _viz._ the
_Keuper_, _Muschelkalk_, and _Upper Bunter Sandstein_, of the German
geologists.
_Subdivisions_:--
1. Variegated red, blue, and white marls, and shales, with gypsum
and beds of rock-salt. (_Marnes irisées_ of the French.)
2. Variegated red and white sandstones.
3. Conglomerates formed of the detritus of the older rocks.
4. Bed mottled sandstone, and marls. (_Grès bigarré_ of the French.)
_Obs._--To this formation belong the principal deposits in
Leicestershire and other midland counties of England. Fossils are
not generally abundant, but some localities yield highly interesting
remains. The shelly limestone of Germany, called Muschelkalk, which
contains the _Lily Encrinite_, &c. does not occur in England. Remains
of Conifers allied to the Yew and Araucaria, are found near Coventry;
and peculiar reptiles (_Labyrinthodons_) near Warwick.
Palæozoic Epochs.
The Permian Formation. (_Wond._ p. 533). The separation of the strata
now termed _Permian_ from the _Triassic_, with which they were formerly
classed, was first proposed by Sir Roderick Murchison, and is based on
the fact that the fossils hitherto discovered are entirely distinct
from any that occur in the Trias and subsequent formations; it is,
therefore, inferred, that after the deposition of the so-called Permian
strata, a complete change took place in the faunas and floras of the
lands and seas, and the Trias is _at present_ regarded as the dawn of a
new system of organic beings.
The strata comprised in this group are variegated blue and red marls
and sandstones, like those of the Triassic; magnesian or dolomitic
limestones; and conglomerates more or less coloured with peroxide of
iron.
_Subdivisions_:--
1. Red and white marls.
2. Yellow magnesian limestones, and dolomitic conglomerates of
Yorkshire and Durham.
3. Marl-slate in thin layers, containing reptiles and fishes. The
Keuper schiefer or copper-schist of Mansfeld.
4. Marls and variegated sandstones, sands, and clays.
_Obs._--This group includes the _Lower Bunter_, _Zechstein_, and
_Rothliegendes_[21] of the German geologists. The _Permian_ comprises
all the deposits that intervene between the Triassic above, and the
Carboniferous below; and it is believed that this formation contains
but one type of animal and vegetable life.
[21] Signifying _Red-dead-layer_; it is a German mining term denoting
that the copper of the upper bed has died out; this layer not being
metalliferous.
The Carboniferous, or Coal Formation. (_Wond._ pp. 660-748).
Sandstones, grits, shales, layers of ironstone, and clay, with immense
beds of coal; fresh-water limestones sparingly; marine limestones
abundantly.
_Subdivisions_:--
1. _The Coal Measures._--Sandstones, shales, and grits, with
numerous beds and seams of Coal; ironstone nodules. Land
plants in profusion. Intercalations of bands of limestone with
fresh-water bivalves and crustaceans in some districts; and with
marine shells in others.
2. _Millstone Grit._--Sandstones, shales, and quartzose
conglomerates and grit, (_provincially_, Millstone-grit): with
shales and thin seams of coal, and plants of the coal-measures
in some localities. The conglomerates and grits have evidently
resulted from the destruction of granitic rocks.
3. _Carboniferous_, or _Mountain Limestone_.--A series, nearly
1,000 feet in thickness, of limestones and flagstones, abounding
in crinoideans, corals, and marine shells and crustaceans;
with layers and nodules of chert. Ores of lead, zinc, copper,
barytes; fluor spar, &c. Limestones, with innumerable shells
of the genera Productus, Spirifer, Goniatites, Orthocera,
Bellerophon, &c. Several varieties of black, bluish grey, and
variegated marbles. Coal occurs in the mountain limestone of
some parts of Russia.
_Obs._--The strata comprised in the carboniferous (coal-hearing)
system, consist of sandstones more or less felspathic, and of
dark bituminous shales with innumerable ferns, and other vascular
cryptogamiæ, and coniferæ, &c. The uppermost group is composed of
numerous alternations of coal, clay, shale, ironstone, and sandstone;
the middle, of sandstones, shales, clays, and quartzose conglomerates,
generally of a dull red colour; and the lowermost, of crystalline
limestones with occasional layers of chert, abounding in marine
shells, corals, crinoidea, and other exuviæ. These lower limestones
are the principal repositories of the lead ores of Derbyshire.
The Devonian or Old Red Formation. (_Wond._ pp. 204 and 751).
Conglomerates, quartzose grits, sandstones, marls, and limestones;
the prevailing colour is a dull red. Shells, corals, and ganoid
fishes, of a very peculiar type. Reptiles, (Telerpeton; _Batrachians?_
_Chelonians?_); the most ancient reptilian remains hitherto discovered.
_Ferns_, _Lepidodendrons_, and other trees of the carboniferous flora;
fluviatile plants with batrachian ova(?).
_Subdivisions_:--
1. Sandstone, quartzose conglomerates, and shale, with but few
fossils.
2. Flagstones, marls, and concretionary limestones; provincially
termed _corn-stones_; laminated reddish and greenish micaceous
sandstones (_prov. tilestones_). Peculiar genera of fish;
orthocerata, and many species of marine shells.
_Obs._--The term Devonian, by which the series of strata comprehended
in this formation is now generally distinguished by geologists, was
first proposed by Sir R. Murchison, as being more precise than the
name formerly applied to this group. In Scotland, where the formation
is of vast extent, it was first characterized by its peculiar ganoid
fishes (Pterichthys, Coccosteus, Cephalaspis), and will probably
always there retain the original name of Old Red.[22] In Devonshire
it is marked by the presence of shells of a character intermediate
between those of the Silurian and Carboniferous systems.
The sandstones are in various states of induration, and when slaty,
are employed for roofing. The red colour predominates in the marls,
and is derived from peroxide of iron. The formation of these rocks
has manifestly resulted from the waste of ancient slate rocks, the
detritus of which is cemented together into coarse conglomerates. In
South Devonshire (at Torquay, Babbicombe, &c.), beautiful coralline
marbles occur in this formation.
[22] See the charming volume of Mr. Hugh Miller, entitled "The Old Red
Sandstone, or New Walks in an Old Field."
The Silurian System. (_Wond._ p. 765). Marine limestones, sandstones,
shales, and calcareous flagstones, characterized by peculiar types
of corals, crinoideans, mollusks, and crustaceans, constitute this
important and extensive system of rocks; the _Grauwacké_, or Transition
series of the earlier geologists.
_Subdivisions_:--
UPPER SILURIAN.
1. _Ludlow rocks_;--slightly micaceous grey-coloured sandstones.
Blue and grey argillaceous limestones. Dark-coloured shales and
flagstones, with concretions of earthy limestone, containing
marine shells, Orthocerata, Spirifers, and Trilobites. _Fishes._
2. _Wenlock_, or _Dudley limestone_;--sub-crystalline blue and grey
limestone, abounding in Trilobites, Crinoidea, Polyparia,
Spirifers, Orthocerata, &c.
3. _Wenlock shale_;--dark grey argillaceous shale, with nodules of
sandstone.
LOWER SILURIAN.
1. _Caradoc sandstone_;--shelly limestones, and finely laminated,
slightly micaceous, greenish sandstones. Corals, Shells,
Trilobites.
2. _Llandeilo flags and limestones._ Freestone, conglomerates,
grits, and limestones. Dark-coloured flags. Beds of schist with
abundance of Trilobites and shells. The lowermost beds are full
of small bivalves, termed _Lingulæ._
_Obs._--The _Silurian System_, (so named by Sir R. Murchison, from
the _Silures_, the ancient Britons who inhabited those parts of our
island in which the geological relations of these strata were first
recognised by him,) occupies the border counties of England and
Wales, and spreads over a vast area of both North and South Wales,
intervening between the Carboniferous series and the Cambrian or
ancient slate-rocks of that country.[23] The strata are entirely of
marine origin, and many of the beds (as the well-known Dudley or
Wenlock limestone) are composed of shells, corals, crinoideans, and
remains of that remarkable family of crustaceans termed Trilobites,
cemented together by carbonate of lime. A few remains of Fishes occur:
Reptiles are unknown. No vegetable relics, excepting _Fuci_, have been
found in Britain below the _Devonian_ or _Old Red formation_.[24]
[23] "The Silurian System, founded on Geological Researches in the
Border Counties of England and Wales." In two parts, royal 4to., with
map, sections, &c., by Sir R. I. Murchison, G.C. St.S. &c. In studying
the beautiful map which accompanies the work, it must be borne in
mind that ten years have elapsed since Sir R. Murchison abrogated
the boundary line that separates the Cambrian and Silurian rocks
in this chart, from the conviction that those deposits constitute
but one natural system (see _Wond._ p. 80.3). For an account of the
Silurian rocks of other countries, see "Geology of Russia," by the same
Author. A summary of the characters of the Silurian System, by Sir R.
Murchison, is given in _Geolog. Journal_, vol. viii. pp. 173-183.
[24] "The Silurian System" contains excellent figures of all the organic
remains known at the period of its publication.
The Cambrian Formation. This term is applied to a largely developed
series of unfossiliferous slate-rocks and conglomerates, many thousand
yards in thickness.
_Obs._--Certain beds of dark-coloured schists containing a few
corals, fuci, and shells, are referred to the uppermost part of this
formation by some eminent geologists, but it is more consonant to the
established system of classification to regard these fossiliferous
beds as the lowermost of the Silurian rocks. The fineness of grain,
general aspect, hardness, and texture of these strata, are well
known, from the general employment of slate for economical purposes.
These rocks extend over a great part of Cumberland, Westmoreland, and
Lancashire, reaching to elevations of 3,000 feet, and giving rise to
the grand scenery of the Lakes, and of North Wales.
Hypogene Rocks. (_Wond._ p. 806.)
_Non-fossiliferous._
Metamorphic (_transformed_) or stratified crystalline rocks.
_Subdivisions._--
1. _Mica-schist System._ (_Wond._ p. 843.) Probably sedimentary
rocks altered by high temperature. Mica-slate, Quartz-rock,
Crystalline limestone, Hornblende schist, &c.
2. _Gneiss System._ Layers of Gneiss, Sienite and Quartz-rock,
alternating with Clay-slate, Mica-schist, &c.
Plutonic Rocks; unstratified crystalline masses.
_Granitic System._ (_Wond._ p. 844.) Granite--a rock composed of mica,
quartz, and felspar; Porphyry; Serpentine; Trap. These rocks occur in
amorphous or shapeless masses, and in dykes and veins.
_Obs._--No fossils have been detected in these rocks: but the intense
igneous action which the masses appear to have undergone, may have
obliterated all evidence of animal and vegetable structures, should
any have been present, as well as the lines of stratification. By
the aid of the microscope, we may yet perhaps solve the mystery
which shrouds the origin of these rocks, and the student may take
up the investigation with the certainty of obtaining much valuable
information, even should the search for organic structures prove
abortive. It is not, however, improbable that the siliceous frustules
of diatomaceæ may have escaped destruction, and remain to reward the
researches of some skillful and patient observer.
Volcanic Rocks. (_Wond._ p. 815.)
The products of subterranean fire or heat, erupted from profound depths
through fissures in the Earth's crust, whether in ancient or modern
times.
_Subdivisions._--
1. _Trap, Basalt, Toadstone, Volcanic-tuff_; the erupted materials
of ancient extinct volcanoes.
2. _Lavas, Scoriæ, Pumice, Ashes_; ejected by modern volcanoes.
_Obs._--These igneous products are of all ages, and they traverse
alike the hypogene rocks and the older and newer sedimentary deposits.
Their characters, and the effects they have produced, are considered
in the work to which reference is made.
* * * * *
By a reference to the geological map of England (_Wond._ pl. i.
vol. i.), it will be seen, that the several formations appear on
the surface in a somewhat chronological order, as we pass from the
eastern or south-eastern part of the Island to the west or north-west.
Thus the principal Tertiary deposits are situated in the eastern
and south-eastern parts; and proceeding towards the north-west, we
traverse successively the _Secondary_--the _Chalk_, _Oolite_, _Lias_
and _Trias_; then the _Palæozoic_--_Permian_, _Carboniferous_,
and _Devonian_; next the _Silurian_ and _Cambrian_; and at length
_metamorphic_ and _primary_ rocks appear. It is this distribution
of the strata of the respective formations that has determined
the characters of the physical geography of England. The Alpine or
mountainous districts, which extend north and south along the western
portion of England and Wales, from Cornwall to Cumberland, are formed
by the elevated masses of the Silurian, Cambrian, and Metamorphic
rocks. These are succeeded by a band of the Carboniferous and Triassic
deposits, with a few intrusions of metamorphic and plutonic rocks, that
stretches from the coast of Devonshire, through the midland counties,
by Leicestershire and Derbyshire, to Newcastle. On the south-east
of this tract, the Oolite and Cretaceous formations, chiefly made
up of argillaceous and calcareous strata, constitute a diversified
agricultural district, extending from the southern shores of Hants and
Dorset to the coast of Yorkshire. The Wealden occupies the country
lying between the Chalk Downs of Sussex, Hants, Surrey, and Kent. The
Tertiary deposits lie in basins or depressions of the upper cretaceous
rocks in the south-eastern and eastern maritime districts, and on an
extensive area of these beds stands the metropolis of England; lastly,
irregular accumulations of Drift, containing mammalian remains in some
localities, are spread over the surface of the ancient formations, and
form the immediate subsoil of the most fertile regions.
CHAPTER III.
ON THE NATURE OF FOSSILS, OR ORGANIC REMAINS.
Fossils; Petrifactions.--It is very generally the case, that persons
who are not conversant with the nature of organic remains, suppose
that all fossils are petrifactions; and unless a specimen has the
aspect and hardness of stone, they regard it as of modern origin, and
devoid of interest. Hence they are surprised to find among the choicest
treasures in the cabinet of the geologist, shells and corals as perfect
in form, as if recently collected from the sea-shore; bones as little
changed, as if they had been interred but for a short period; and
teeth possessing their sharp edges and enamel unimpaired. In my early
researches I fell into this error, and threw away many beautiful shells
that were associated with casts of ammonites in the marl at Hamsey,
supposing, from their perfect state, that they had been accidentally
imbedded, and were not genuine fossils. But the state of preservation,
and the degree of change which an organic body has undergone in the
mineral kingdom, have no necessary relation to its antiquity. The
shells in some of the ancient secondary strata are frequently as little
changed as those in modern tertiary deposits. I have collected from the
lowermost clays of the Wealden, fresh-water shells with traces of the
epidermis, and the ligament by which the valves were held together,
perfect; and bones of reptiles from the strata of Tilgate Forest, as
light and porous as those of the bears and hyenas, from the Caverns of
Germany. On the other hand, fossil remains from the newest tertiary
formations are often completely petrified, that is, permeated by, or
transmuted into, stone.
The words _fossil_ and _petrifaction_ are so commonly used as
synonymous terms, even by educated persons, that it is necessary to
define the sense in which they are employed in these volumes.
_Fossils_ are the durable parts of animal and vegetable structures
imbedded in rocks and strata by natural causes at a remote period; thus
wood in a state of lignite, bog-wood, and coal, or of siliceous or
calcareous stone, is _fossil wood_; and bones or shells, whether in an
earthy and decaying state, or permeated by calc-spar, flint, or iron,
and converted into a hard mineral substance, are alike _fossil bones_
or _shells_.
_Petrifactions_ are the remains of animals and vegetables in which
the original structure is converted into stone, or, in other words,
is _petrified_; such are the silicified stems of trees from Antigua,
and Germany, and the calcified bones and shells in the Oolitic and
Wealden limestones. Such petrifactions may be correctly termed fossil
plants, bones, or shells; but similar organic remains, though of equal
antiquity, which have not undergone such changes, are not petrifactions
in the proper meaning of that term.
The process by which petrifaction is effected is still involved in
obscurity; mineral solutions have permeated the original tissues,
and the organic molecules have been replaced by mineral molecules,
but how this transmutation is produced is not understood. Mr. Dana's
observations and Mr. Jeffery's experiments have, however, thrown much
light on the process of silicification.[25]
[25] See _Wond._ p. 100.
_Incrustations._--Another prevalent error is that of considering
Incrustations to be fossils or petrifactions; a mistake which is
sanctioned by the custom of calling waters that are charged with
calcareous earth (_lime_), and deposit it in considerable quantity,
petrifying springs; as those of Matlock, and other places in
Derbyshire. (_Wond._ p. 76.) But incrustations are not petrifactions;
stems and branches of trees, skulls, bones, shells, &c., are simply
invested with a calcareous coating or crust, which is generally porous
and friable, but often crystalline and compact. The inclosed bodies
are not permeated by the stony matter; if the mass be broken, or
the incrustation removed, we find the twig, or stem, either dry and
shrivelled, as in the specimens, figs. 2, 3, 4, Plate III.; or tubular
cavities are left by the decay and removal of the vegetable structure,
as in fig. 10, Plate III.
But although incrustations be not petrifactions, natural specimens,
(not the so-called petrified nests and twigs, in which the bad taste of
the guardians of the Derbyshire springs is embodied, and dispersed all
over England,) are objects of considerable interest, as illustrative
of a process, by which important changes are effected in the mineral
kingdom. Thus springs as clear and sparkling as poet ever feigned or
sung, may transform beds of loose sand and gravel into rock, and porous
stone into solid marble, and cover extensive tracts of country with
layers of concretionary and crystalline limestone. This process is
effected in the following manner. Most fresh water holds in solution a
certain proportion of carbonate of lime; and changes of temperature, as
well as other causes, will occasion this calcareous earth to be in part
or wholly precipitated. The _fur_, as it is called, that lines a kettle
or boiler which has been long in use, affords a familiar illustration
of this fact. At the temperature of 60° lime is soluble in 700 times
its weight of water; and if to the solution a small portion of carbonic
acid be added, a carbonate of lime is formed, which is thrown down
in an insoluble state. But if the carbonic acid be in such quantity
as to supersaturate the lime, it is again rendered soluble in water:
it is thus that carbonate of lime, held in solution by an excess of
carbonic acid, not in actual combination with the lime, but contained
in the water, and acting as a menstruum, is commonly found in all
waters. An absorption of carbonic acid, or a loss of that portion which
exists in excess, will therefore occasion the lime to be set free, and
precipitated on the foreign bodies in the water, as stones, twigs,
leaves, &c.
The substance thus deposited is termed _tufa_, or travertine;[26] and
in some parts of Italy, and of our own Island, it constitutes beds of
stone of great extent, in which bones, shells, and the impressions of
leaves and stems, are preserved. The stalactites and stalagmites of
caverns have a similar origin; many of these caves are of incalculable
antiquity, and beneath their stalagmitic floors, the bones and teeth of
extinct carnivorous animals are found in vast quantities.
[26] _Travertine_, so called from the river _Tibur_, whose waters are
loaded with calcareous earth--_Tiburtina_, Ital. _travertina_.
Silicification, or petrifaction by Silex or Flint.--Silex, or the earth
of flint, is held in solution in large proportions, in certain thermal
or boiling springs, which, on cooling, deposit the siliceous matter
(in the same manner as the travertine is precipitated from incrusting
streams) on foreign substances, and produce exquisite chalcedonic
infiltrations of mosses, &c. But this operation is now only known to
be in activity in the immediate neighbourhood of foci of volcanic
action, as in the celebrated Geysers of Iceland (_Wond._ p. 95), and
the boiling springs of the volcano of Tongariro, in New Zealand (98).
We have everywhere evidence that in former periods, the petrifaction,
as well as the incrustation of organic bodies by silex, was carried on
to an immense extent; and, doubtless, far beneath the surface, the same
operation is at the present moment in constant progress, and effecting
as important changes in the consolidation of loose materials, as in the
earlier geological epochs.
The various states in which silex occurs have depended on its fluidity;
in quartz crystals the solution appears to have been complete; in agate
and chalcedony it was in a gelatinous state, assuming a spheroidal or
orbicular disposition, according to the motion given to its particles.
Its condition appears also to have been modified by the influence
of organic matter. In some polished slices of siliceous nodules the
transition from flint to agate, chalcedony, and crystallized quartz, is
beautifully shown. The curious fact, that the cavities of echinites in
chalk are almost invariably filled with flint, while their crustaceous
cases are changed into calc-spar, is probably, in many instances, to
be attributed to the animal matter having undergone silicification;
for the soft gelatinous parts are those which appear to have been most
susceptible of this transmutation. In some specimens, the oyster is
changed into flint, while the shell is converted into crystallized
carbonate of lime. In a Trigonia from Tisbury, formerly in the cabinet
of the late Miss Benett, of Norton House, near Warminster, the body
of the mollusk was completely metamorphosed into a pure chalcedony,
the branchiæ or gills being as clearly defined as when the animal was
recent. In specimens of wood from Australia (presented to the British
Museum by Sir Thomas Mitchell), which are thoroughly permeated by
silex, there are on the external surface some spots of chalcedony that
have apparently originated from the exudation of the liquid silex from
the interior in viscid globules filled with air, which burst, and then
collapsed, and became solidified in their present form.
In silicified wood the permeation of the vegetable tissues by the
mineral matter, appears to have been effected by solutions of silex of
a high temperature. In some examples the mineralization is simply a
replacement: the original substance has been removed atom by atom, and
the silex substituted in its place.
One of the most eminent naturalists and chemists of the United States,
Mr. Dana,[27] suggests that the reason why silica is so common a
material in the constitution of fossil wood and shells, as well as in
pseudo-morphic crystals,[28] is the ready solution of silex in water
at a high temperature (a fact affirmed by Bergman[29]) under great
pressure, whenever an alkali is present, as is seen at the present
time in many volcanic regions, and its deposition again when the water
cools. A mere heated aqueous solution of silica, under high pressure,
is sufficient to explain the phenomenon of the silicification of
organic structures. Mr. Dana states that a crystal of calc-spar in
such a fluid being exposed to solution, from the action of the heated
water alone, the silica deposits itself gradually on a reduction
of temperature, and takes the place of the lime, atom by atom, as
soon as set free. Every silicified fossil is an example of this
pseudo-morphism; but there seems to be no union of the silica with the
lime, for silicate of lime is of rare occurrence.[30]
[27] American Journal of Science for January 1845.
[28] Pseudo-morphic crystals are crystals moulded in the cavities
left by other crystals which they have replaced. See Dr. Blum on
Pseudo-morphous minerals.
[29] Bergman first determined the solubility of silex in simple water,
aided by heat, and demonstrated its existence in the Geysers and other
boiling springs of Iceland.--_Parkinson, Org. Rem._ vol. i. p. 324.
[30] See my "Notes on a Microscopical Examination of Chalk and Flint,"
Annals of Natural History, August 1845.
* * * * *
I proceed to consider the various states in which the remains of
animals and plants are preserved in the mineral kingdom, and shall
occasionally offer suggestions for collecting and preparing specimens;
but particular instructions on this head will be given in the sequel,
when the different kinds of fossils are respectively considered.
[Sidenote: FOSSIL ANIMAL REMAINS.]
Animal Remains.--Of the higher orders of animals, the more durable
portions of the skeleton, as the bones and teeth, are almost the
only parts that occur in a fossil state; except in some remarkable
instances, in which entire carcasses of extinct species of Elephant,
and of Rhinoceros, have been found imbedded in solid ice, and frozen
gravel. (_Wond._ p. 152.) The countries of arctic regions are now the
only localities in which such phenomena are likely to be met with;
it appears, however, that in some remote period, the bodies of large
mammalia were transported by icebergs into temperate regions, where
the ice melted, and the animals either sunk to the bottom of the sea,
or were drifted into estuaries, or stranded on the shore: the soft
parts then decomposed, and the skeletons and detached bones were left
imbedded in the silt, sand, or shingle.
In this manner alone can be explained the occurrence of bones and teeth
of the mammoth, rhinoceros, hippopotamus, &c. so common in the alluvial
or drifted deposits of this country; for these relics, though extremely
friable, and buried in shingle, boulders, and other transported
materials, are not water-worn, but in numerous instances remain as
sharp and perfect as when recent. In the ancient shingle of Brighton
cliffs (_Wond._ p. 114), I have found bones and teeth of horse, deer,
ox, whale, &c. impacted with quartz and granite pebbles and boulders;
the bones, though crumbling to pieces if not very carefully removed,
being entire, and the whole mass held together by calcareous spar,
deposited by water that had, during the lapse of ages, percolated
through the chalk-rubble above.
Fossil bones are found in four different states: 1. With their animal
matter, as in the bones of the Mastodons from Big-bone Lick, Kentucky.
2. With the animal matter removed. 3. With the earthy matter partly
removed, 4. With the animal matter carbonized, or converted into
bitumen; this change is common in the blue Lias clay; the bones retain
their usual quantity of phosphate of lime, but the animal matter is
converted into carbon. This alteration appears to have taken place
unconnected with a high temperature, and to have been a spontaneous
change in a moist situation, to which air had no access.[31]
[31] Mr. Smee, London Med. Gazette, November 1840.
Another, and very remarkable condition, is that in which the phosphate
of lime has been removed by the infiltration of water charged with
sulphuric or carbonic acid, and the gelatin converted into leather
by tannin; as is the case with bones and teeth of deer, horses, &c.
obtained from a submerged forest of oak, larch, &c. near Ferry-bridge,
in Yorkshire; of which there are many instructive specimens in the York
Museum.[32]
[32] Communicated by Professor John Phillips.
The cancellated structure (that is, the little cells or pores) of
the long-bones of mammalia, found in caverns in England and Germany,
and in the breccia of Gibraltar, and the conglomerates of Ava and
the Sub-Himalaya mountains, &c., are often filled with crystallized
carbonate of lime. In the Wealden deposits the osseous carapaces and
plastrons of Turtles, and the bones and teeth of Crocodiles, Lizards,
&c., are almost without exception heavy, and of various shades of brown
or umber, from the infiltration of solutions of carbonates and oxides
of iron.
In some instances, bones of a jet black are imbedded in the white
calciferous grit; the phosphoric acid in the original organism having
combined with iron and produced a deep blue or black phosphate of that
mineral, and left the surrounding stone uncoloured.
Petrifaction by the infiltration of calcareous solutions is equally
common; and the medullary cavities of the bones are frequently lined
or filled with white calc-spar; brilliant pyrites also enters into the
composition of these fossils, frosting over with a golden metallic
deposit the cavities and fissures.
[Sidenote: FOSSIL BONES.]
The permeation of the teeth by mineral matter, produces beautiful
examples of the tissues of those organs; the dentine is often stained
throughout with a rich sienna tint, and sections viewed under the
microscope by transmitted light, reveal the character and distribution
of the calcigerous tubes more clearly even than in recent specimens.
It is extremely rare that osseous structures are found petrified by
flint; among the many thousands of bones which I have extracted from
the rocks, or have seen in collections, I know but of one instance of
a silicified vertebra, that of a Mosasaurus, from a chalk-pit near
Brighton; and a few bones and scales of fishes. But notwithstanding the
weight and apparent solidity imparted by these modes of mineralization,
the substance is generally rendered extremely brittle, so that the
development of the bones from the stone in which they are imbedded,
and the removal of the hard ferrugino-calcareous crust investing them,
is no easy task, but requires much tact, experience, and patience, to
execute successfully.
Hints for collecting fossil bones.--The light, friable, porous bones,
require great care in their removal from the deposit in which they
are imbedded, whether it be clay, consolidated shingle, or limestone;
if of considerable size, they will almost invariably break to pieces,
and many examples will not admit of repair. It is therefore always
desirable, before attempting to extract a large bone, to make a sketch
of it; its form will thus be known, should it be destroyed; and if it
crack into fragments that will admit of reunion, the drawing will be a
valuable guide for the replacement of the separated parts. If only a
few pieces remain, those which show any portion of the terminations,
or joints, should be preserved, as they afford the most precise and
important characters. The faithful record even of an imperfect and
unknown fossil is not without value; and as the antiquary carefully
preserves shreds of ancient manuscripts, in the hope that other
documents may one day come to light, and enable him to interpret these
now unintelligible records; so the geologist should treasure up every
fragment of an undetermined organic remain, for the time may arrive, as
I have often experienced, when specimens will be discovered that may
illustrate its nature, and prove it to be of considerable interest.
The broken porous bones may be easily repaired by a hot weak solution
of glue; and when the joinings are set, the bone should be saturated
with thin glue, well brushed in, and the surface be sponged clean with
very hot water before the cement is congealed. When dry, the specimens
will be found to possess considerable firmness and durability.[33]
By this process the tusks of mammoths and elephants may be restored,
however much crushed; time, patience, and a little dexterity, only are
required, to convert a heap of mere fragments into a valuable relic of
the ancient world.
[33] A liquid, called "Neuber's liquid glue," is an excellent cement
for this purpose: it is sold at No. 54, New Oxford Street, London.
When the bones are tolerably perfect, but dry and friable from the
loss of their animal oil, they may be made durable by saturating
them with drying oil, and exposing them to a considerable degree of
heat; in this manner the magnificent skeletons of the sloth tribe,
the Megatherium, and Mylodon, in the Hunterian Museum, were prepared.
When a bone appears as if cracked into numerous pieces before its
removal, but still preserves its form, the only method by which it can
be successfully extracted, is by spreading over it a thick layer of
plaster of Paris, which should be used of the consistence of cream;
when it sets, (which, if the plaster be recently prepared, will be in
the course of a few minutes,) the specimen may be carefully extricated,
and the plaster removed or not, according to the nature of the fossil,
and the parts to be displayed. The bones of the large reptiles which
occur in the Wealden and Oolite, may be restored in the same manner.
These remains are generally very brittle, and when imbedded in hard
grit cannot be extracted whole: they will often fall to pieces on the
slightest blow of the hammer or chisel. When of moderate size, it is
best not to attempt their removal from the stone, but to trim the block
into a convenient shape, and carefully chisel away the surrounding
part, so as to expose the essential characters of the bone. In all
cases this is an excellent method where practicable, for such specimens
have a double interest; they are at once illustrative examples of the
fossil, and of the rock in which it was deposited.
But many specimens will not admit of this method; and with large
ones it is inconvenient and undesirable, except where bones lie in
juxtaposition. The large examples in Tilgate grit, (figured in the
Fossils of Tilgate Forest,) were all extracted piecemeal from the rock:
and most of the gigantic bones of the Iguanodon, &c. now in the British
Museum, were originally in many hundred pieces, and were cemented
together with glue in the manner above described; I have found no other
method so convenient and effective.
When a bone is too imperfect to be united as a whole, it may be
imbedded in Roman cement, or plaster of Paris, which when dry may be
coloured of the prevailing tint of the rock. For large heavy specimens,
the cement is preferable; it is of easy application, and the fissures
and cracks of the bones may be filled up with it, taking care first to
cover the parts with thin hot glue, or the cement, when it dries, will
shrink and fall out. A thin coating of mastic varnish will restore the
colour, and by excluding the air, tend to preserve the specimens.
The teeth have generally undergone the same changes as the bones with
which they are associated. The teeth of elephants or mammoths that are
imbedded in loose calcareous earth, like the loam and chalk-rubble of
Brighton cliffs, and of Walton in Essex, are friable, and apt to split
and separate in the direction of the vertical plates of dentine and
bone: the pieces should be glued together, and when set, the tooth be
thoroughly saturated with thin glue, used very hot, and the superfluous
cement removed with a sponge wrung out as dry as possible from boiling
water. If there be any portion of the jaw attached to the teeth, it
must be carefully preserved; and search should be made for fragments of
the articulations, or parts of the joints and sockets.
In argillaceous strata, as the Lias-shale, London Clay, &c., the
fossils are frequently saturated with brilliant pyrites, or sulphuret
of iron; a mineral which decomposes upon exposure to the atmosphere,
and occasions the destruction of the specimens. The fossils of the Isle
of Sheppey are peculiarly obnoxious to this change.
[Sidenote: FOSSIL ANIMAL REMAINS.]
The remains of vertebrated animals in the Lias, very often occur
as skeletons more or less perfect, the entire configuration of
the original being preserved in many instances (_Bd._ pl. 7.
_Petrifactions_, p. 340). But the deposit in which they lie is
generally laminated, and the shale flakes off without great care; much
time, labour, and practice are therefore required, to obtain specimens
of any considerable size. To the late Miss Mary Anning, of Lyme Regis,
the merit is due, of having first accomplished this difficult task;
Mr. Hawkins has subsequently carried the art to perfection, as may be
seen in the marvellous examples of Ichthyosauri and Plesiosauri, in the
British Museum.[34]
[34] Petrifactions, Room IV. chap. iv. pp. 341, 376.
The small specimens, such as the detached paddles, groups of vertebræ
and ribs, &c., that are likely to come under the collector's notice
in his personal researches, are not difficult of preservation. Mr.
Hawkins employed a strong watery solution of gum arabic as the cement,
and plaster of Paris as the ground, using shallow wooden trays of
well-seasoned wood, in which the specimens were permanently imbedded:
the bones, scales, &c. were then varnished with a solution of mastic,
and the ground coloured bluish grey, to imitate the Lias. I have had
considerable practice in the dissection of skeletons imbedded in Lias,
and having found the method previously described answer every purpose,
have not employed that recommended by Mr. Hawkins.
The scales of reptiles and fishes, either in connected masses or
detached, are frequently met with in great perfection, and sometimes
associated with the teeth and bones. In the Lias, even the remains
of the skin and integuments (_Bd._ pl. 10) have been discovered.
Whenever any part of a skeleton is found lying in shale or stone,
the surrounding block should therefore be carefully examined, to
ascertain if there be traces of the skin or integuments, before any
part is removed by the chisel. The specimen of an Ichthyosaurian
paddle, figured in the second volume of this work, affords a good
illustration of the propriety of this caution. Around the bones are
seen the carbonized remains of the cartilaginous fringe that supported
the integuments, and thus the perfect form of the paddle has been
ascertained; had the surrounding stone been chiselled away, the most
important characters would have been obliterated, as probably they have
been in numerous instances.
Nodular masses of indurated clay containing fishes, are often broken
with difficulty in such a manner as will expose the enclosed fossil,
for the nodule generally splits in various directions, and the specimen
is irreparably mutilated or defaced. My friend Sir Woodbine Parish
informs me that by subjecting such nodules to a high temperature--but
not to a red heat--and then plunging them in cold water, they may when
dry, by a properly directed blow of a hammer, be readily fractured in a
direction parallel with the plane of the imbedded fossil, and the fish
be laid bare in the most favourable position.
The scales of fishes, and the integuments of marine reptiles, are not
the only vestiges of the dermal coverings of vertebrated animals that
are preserved by mineralization. Traces of the wing-integument of
flying reptiles, and of the feathers of birds, are sometimes manifest:
and even when every atom of the original structure has perished, the
impression may remain, and afford satisfactory results. The footmarks
of unknown animals are often preserved in the rocks, and the imprints
of the feet of several species of bipeds, presumed to be birds of
colossal size, in tracks as distinct as if but recently made, have been
discovered in the New Red sandstone of North America; in the section on
fossil birds, this highly interesting subject will be fully explained.
The student, even from this brief review, will perceive how many
valuable facts may be unnoticed, and irretrievably lost, unless
attention be paid to the various circumstances under which fossil
remains are presented to his notice.
Of the invertebrated orders, the most durable, and consequently the
most numerous relics, are shells and corals. The integuments of the
eyes, antennæ, and wings of Insects occur; and the shelly coverings
of Crustaceans are not uncommon; those of the Echinoderms, the
Star-fishes, and of the Crinoidea or Lily-animals, are very abundant in
certain deposits. Instructions for the collection and arrangement of
these fossils will be given in the chapters in which they are severally
described.
PART II.
⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼
CHAPTER IV.
FOSSIL BOTANY.
Fossil Vegetables.--The remains of the vegetable kingdom are presented
to the notice of the geologist in various conditions; in some instances
these relics are but little changed in their aspect, as, for example,
in the recent accumulations of mud and silt, at the bottoms of lakes
and rivers, and in morasses, and peat-bogs. In tufaceous incrustations,
the imprints of wood, and of leaves and stems, are often sharply
defined on the solid masses of concretionary and crystalline limestone.
In the ancient deposits, vegetables are found in two different states.
In the one their substance is completely permeated by mineral matter;
it may be calcareous (_lime_), siliceous (_flint_), ferruginous
(_iron_), or pyritous (_sulphuret of iron_); and yet both the external
characters, and the internal structure, may be preserved. Such are the
fossil trees of the Isle of Portland, fragments of which so closely
resemble decayed wood, as to deceive the casual observer, until by
close examination of their texture and substance he finds that they
possess the weight and hardness of stone. In the silicified wood which
abounds in many of the tertiary strata, the most delicate tissues of
the original are preserved, and by microscopical examination (see Pl.
V.) may be displayed in a distinct and beautiful manner. In calcareous
fossil wood the structure is also retained; and in many limestones,
leaves and seed-vessels are well preserved.
The ligneous coverings, or the husks and shells, of nuciferous fruits,
and the cones or strobili of Firs and Pines, are frequently met with in
an excellent state of preservation; in some rare instances indications
of flowers have been observed (_Lign. 67_). The parts of fructification
in some of the fern tribe (_Lign._ 25 and 27), occur in coal-shale,
and in the grit of Tilgate Forest (_Wond._ p. 394): the pollen, and the
resinous secretions of pines and firs, have been discovered in tertiary
marls, and in the Greensand. The well-known substance. Amber, so much
in request for ornaments, is unquestionably of vegetable origin; it has
been found impacted in the trunks of its parent trees (_Wond._ p. 242).
The _fossil resin_ discovered in the London clay, at Highgate and the
Isle of Sheppey, is doubtless referable to the coniferæ found in that
deposit.
In the Clathrariæ of Tilgate Forest, indications of a resinous
secretion have been detected.
The _Diamond_, which is pure charcoal, is probably a vegetable
secretion, that has acquired a crystalline structure by
electro-chemical forces. It has been converted into _Coke_ and
_Graphite_ by the action of intense heat; and the electrical properties
of the substance were changed, the Diamond being an insulator, and the
Coke, a conductor of electricity. (_Wond._ p. 706.)
When the microscope is more extensively employed in investigations of
this kind, it is probable that the siliceous spines and stars which
begem the foliage of many plants (as the _Deutzia_, _Lithospermum
officinale_, &c), will be discovered in a fossil state, for they are
as indestructible as the frustules of Diatomaceæ, and the spicules of
sponges which are so common in flint and chalcedony.
[Sidenote: FOSSIL VEGETABLES.]
But vegetables occur not only as petrified stems, leaves. and fruits,
associated with other remains in the strata, but also in beds of great
thickness and extent, consisting wholly of plants transmuted, by that
peculiar process which vegetable matter undergoes when excluded from
atmospheric influence, and under great pressure, into _Lignite_, and
_Coal_. And there are intermediate stages of this process, in which the
form and structure of the trees and plants are apparent; and a gradual
transition may be traced, from the peat-wood and submerged forests
of modern epochs, in which leaves, fruits, and trunks of indigenous
species are preserved, to those ancient accumulations of carbonaceous
matter, whose vegetable origin the eye of science can alone detect.
For the collection and preservation of fossil vegetables, with the
exception of those which are permeated with. pyrites (as those of
the Isle of Sheppey, &c.), but few instructions are required. The
silicified and calcareous stems are generally easy of extraction, even
when imbedded in hard stone, and if broken can be repaired with glue.
When the stems bear the imprints of leaf-stalks (as in _Lign._ 31 and
54), the surrounding stone should be carefully examined, with the
view of detecting impressions, or other indications of the foliage.
Delicate leaves in clay, or shale, must not be washed; a thin coat of
mastic varnish, or of gum-water, applied with a camel-hair pencil,
will preserve them, and render them more distinct. When a leaf, fruit,
seed-vessel, or other fragile object is attached to clay or friable
sandstone, it is advisable to glue the specimen to a piece of thin wood
or pasteboard, of suitable proportions.
The Sheppey fruits and other fossils permeated with iron pyrites,
generally decompose after a few months' exposure to the air. The
fruits, especially, are liable to decomposition; Mr. Bowerbank keeps
his specimens in bottles of water; a solution of isinglass in spirits
of wine is the best varnish to preserve such fossils, without obscuring
their character and injuring their appearance: but even this method is
often unavailing. The pyritified fir-cones of the Wealden decompose
in like manner: I have had the misfortune to lose several unique and
most instructive specimens from this cause; boiling them in linseed oil
preserves them, but greatly impairs their appearance.
* * * * *
ON THE INVESTIGATION OF THE FOSSIL REMAINS OF VEGETABLES.
Vegetable Organization.--As fragments of the stems, trunks, and
branches, are very often the only vestiges of fossil plants, a
knowledge of the characters by which the principal divisions of the
vegetable kingdom may be distinguished by their internal structure,
is indispensable to the successful investigation of the Flora of the
ancient world. Although I have treated of this subject in the Wonders
of Geology, (_Wond._ p. 694,) it will here be necessary to present the
student with more ample details. The excellent introductory botanical
works of Dr. Lindley, and Professor Henslow, convey full information
on this, and every other department of the science, and should be
consulted by those who intend to make this branch of Geology their
particular study. For the general reader, and amateur collector,
the following brief notice of a few obvious essential characters of
vegetable organization, may perhaps afford sufficient information,
to enable them to understand the principles on which the successful
investigation of the nature and affinities of fossil plants must be
conducted.
[Illustration: Lign. 1.
Sections of Recent Vegetables; illustrative of their internal
organization. (From _Dr. Lindley_.)
Fig. 1.--Longitudinal Section of Coniferous Wood.
_a._ The Ducts,
_b._ Spiral Vessels,
_c._ Glandular vessels.
2.--Transverse section of a dicotyledonous stem.
_a._ Pith, or central column.
_b._ The bark.
_c._ Medullary rays.
_d._ Vascular tissue between the medullary rays.
3.--Elongated cellular tissue, forming the medullary rays.
4.--Transverse section of a monocotyledonous stem.
]
[Sidenote: STRUCTURE OF VEGETABLES.]
Every plant is essentially an aggregation of cells;[35] and the most
simple forms of vegetation consist of a congeries of cells (_cellular
tissue_) of the same kind, and have no visible fructification; such
are the sea-weeds (_algæ_, _conferæ_, &c.), mosses, and lichens. In
the more complex tribes the cells become variously modified, are
elongated into tubes or vessels (_vascular tissue_), some of which
possess a spiral structure, and others have their sides studded with
little glands. The vascular tissue consists of two kinds of vessels.
1. The _spiral vessels_ or _tracheæ_: these are membraneous tubes,
with conical extremities, having within a coil of elastic fibre
spirally twisted, and capable of being unrolled (_Lign. 1, b._).
2. The _ducts_; which are a modification of the structure of the spiral
vessel; their extremities are rounded or conical, and their sides
marked with transverse lines, rings, or bars. Their functions appear to
be different from those of the spiral vessels, and they are found in
situations where the latter never occur.
[35] "A _cell_ in botanical language, means a little bag composed of
membrane, and containing a living substance capable of spontaneous
growth by multiplication, or division of its parts. Of such little
bodies, millions of which may be contained within the space of a cubic
inch, all the soft parts of vegetables are composed; in sea-weeds they
are often of large size."--Dr. Harvey's Sea-side Book, with which the
reader is doubtless familiar.
The organization of the stem in the whole class of flowering plants,
possesses characters so evident, as to afford the most important aid in
the investigation of their fossil remains. Without dwelling on minor
modifications, they are separable into two divisions, namely, the
Endogenous (signifying _to grow from within_), and the Exogenous (_to
grow from without_). Both possess vascular tissue, but so differently
arranged in the two classes, as to constitute distinctive characters
which are seldom obliterated, although what was once a flexible stem,
is now a mass of flint.
Endogenous Stems.--As the seeds of the plants belonging to this
division have but one cotyledon, or _seed-lobe_, as the Lily, they
are also termed monocotyledonous; the reader therefore must remember
that these terms are synonymous. These stems consist of an uniform
mass of cellular tissue, in which bundles of vascular or woody fibre
are imbedded; a transverse section presents a surface dotted over
with spots, produced by the division of these groups of vessels,
pretty uniformly distributed, but more densely arranged towards the
circumference (_Lign. 1, fig. 4_). A slice of cane affords an
illustration of this structure.
The increase of these stems is effected by the formation of new cells
and bundles of vessels in the central axis, which force their way among
the old tissue, and occasion the condensation of the latter towards the
outer edge. These plants have neither pith, concentric circles of woody
fibre, nor true bark; negative characters of the highest importance in
the determination of fossil stems.
Exogenous Stems.--The seeds have two cotyledons, or seed-lobes,
as in the Bean, hence the plants of this class are also called
dicotyledonous. In these stems the cellular tissue forms a central
column, or pith (_Lign. 1, _fig. 2, a_.), and an external band, or
cylinder, called the bark (_fig. 2, b_.); the two being connected by
thin vertical plates, termed medullary rays, which are also formed
of cells (_fig. 2, c, c_.); the diagram, _Lign. 1_, exhibits this
arrangement. The interval between the pith and the bark, and the
interspaces of the vertical radiating plates (_fig. 2, d_.), are
filled up by woody fibre or vascular tissue, consisting of spiral and
other vessels. The ligneous structure of exogenous stems consists,
therefore, of a cylinder formed of wedge-shaped processes, that extend
between the medullary rays to the pith, and is surrounded by the bark;
a new zone of woody fibre is added annually between the bark and the
former cylinder, and from this mode of increase the term _exogenous_
is derived: a transverse section of a branch of oak or ash will show
this structure. The rings, or concentric circles, are the annual zones
of wood; the fine lines radiating from the centre, or pith, to the
circumference, or bark, are the medullary rays (_Lign. 1, fig. 2, c_:
see also _Plate V. fig. 4_).
The organization above described, will be found more or less manifest
in fossil wood, stems, and branches. The monocotyledonous structure is
beautifully displayed in the silicified stems of palms from Antigua
(_Plate V. fig. 1, 1^a._): and the dicotyledonous, in petrified trees
from Egypt. The pith, medullary rays, vascular tissue, and circles of
growth, are preserved in the siliceous and calcareous wood found in
many parts of England.
[Sidenote: STRUCTURE OF CONIFERÆ.]
Structure of Coniferæ (_cone-bearing_).--The remains of a numerous
family of dicotyledonous trees, termed _Coniferæ_, as the pine, fir,
larch, &c., are so abundant in the stratified rocks, that it is
necessary to describe in more detail the peculiarity of structure by
which their stems and branches may be recognised. The most delicate
woody tissue, as we have above stated, consists of elongated cells
or tubes, of two kinds: in the one, the membrane of which they are
composed is smooth: in the other, the walls of the tubes are covered by
little oval or circular bodies called glands (_Lign. 1, fig. 1, c._). A
branch of larch or pine, split longitudinally, and viewed by a powerful
lens, will exhibit the appearance here described. This glandular
structure is so constantly and largely developed in the coniferæ, that
although it is also possessed by other aromatic trees, we shall rarely
err in referring fossil wood in which this organization is apparent,
to this family of vegetables (see _Plate V. figs. 2, 3_). These glands
in the pines and firs, are supposed to be the cells which secrete a
colourless volatile oil, that exudes in the state of turpentine.
From this general account of the vegetable structures that may be
expected to occur in the mineral kingdom, the student will in some
measure be prepared for the investigation of fossil trees and plants;
but for the guidance of those who are wholly unacquainted with the
principles on which the Natural System of Botany adopted in this work,
is founded, I am induced to present the following concise view of the
principal divisions of the vegetable kingdom, though it involves some
repetition.
[Sidenote: BOTANICAL PRINCIPLES.]
The following summary is given nearly in Dr. Lindley's own language:--
Botanical Principles.--One of the first things that strikes an inquirer
into the structure of plants, is the fact, that while all species are
capable of propagating their race, the mode in which this function is
effected is essentially different in different cases. In most tribes
of plants, flowers are produced, and these are succeeded by fruit,
containing seed, which is shed, or scattered abroad, and grows into
new individuals. But in certain families (the _Cryptogamia_), as
Ferns, Mosses, Mushrooms, and the like, neither flowers, nor seeds
properly so called, have been detected; but propagation is effected
by the dispersion of grains or spores, which are usually generated in
the substance of the plant, and seem to have but little analogy with
true seeds. Hence the vegetable kingdom is separated into two distinct
groups, namely, the _flowering_ (_Phanerogamia_), and the _flowerless_
(_Cryptogamia_ or _Agamia_). As the former usually possess a highly
developed system of spiral and other vessels, while the latter are
either altogether destitute of them, or have them only in a few of the
highest orders, and those in a peculiar state, the flowering plants
are termed Vasculares, and the flowerless _Cellulares_. And as all
the flowering, or vascular plants, when they form stems, increase by
an extension of their ends, and a distension or enlargement of their
circumference, but the flowerless or cellular plants form their stems
simply by the addition of new matter to their points, the latter are
called _Acrogens_, signifying increase from the summit.
Flowering plants are also for the most part furnished with respiratory
or breathing organs (_stomata_), of which the flowerless vegetables are
to a great extent destitute.
The flowering or vascular plants are also divisible into two well
marked groups, namely, the _Exogens_, or _Dicotyledons_, and the
_Endogens_, or _Monocotyledons_.
The Exogens (growing from without), increase by the addition of new
woody matter to the outside of the stems beneath the bark; and they are
further characterized by the embryo having two or more cotyledons, or
seed-lobes, hence they are also called _Dicotyledons_; such as the Elm,
Beech, &c.
The Endogens, as we have previously stated, increase by the addition
of ligneous matter to the inside of their stems near the centre; and
as the embryo in this class has but one cotyledon, they are likewise
termed _monocotyledons_, as the Cane, Palm, &c. Again, exogenous
plants have the young external wood connected with a central pith, by
medullary processes; while endogens do not possess such a structure,
having no central pith. In exogens the veins (venation) of the leaves,
are disposed in meshes, like net-work, but in endogens the veins run
parallel to each other.
The number of parts in the flower of an exogenous plant is usually
five, or its multiples: in the endogens it is commonly three, or its
multiples. In the germination, the young root of exogens is a mere
extension of the radicle; but in endogens it is protruded from within.
Thus, in the flowering or vascular plants, we have two groups distinct
from each other in their germination, the structure of their stems
and leaves, their mode of growth, the arrangement of the parts of the
flower, and in the structure of the embryo.
The vegetable kingdom is thus separated into three natural classes,--1,
the _Exogens_, 2, the _Endogens_, 3, the _Acrogens_; but there are
likewise other divisions, a knowledge of which is of great importance
in the study of fossil botany; the sub-class termed Gymnosperms
especially requires notice.
In the strictly exogenous and endogenous plants, the fertilizing
principle is communicated to the young seeds through the medium of a
_stigma_ and _style_, that terminate the case or pericarp in which the
seeds are enclosed: but in another important group of the vegetable
kingdom, the pollen is directly applied to the ovule, without the
intervention of any pericarpial apparatus; hence these are termed
_Gymnosperms_, signifying naked seeds. These plants have the same
relation to the other exogens, as frogs and analogous reptiles bear to
the other orders of their Class; they comprise the two natural orders
_Coniferæ_, and _Cycadaceæ_.
The Gymnosperms also possess peculiarities of a subordinate nature:
thus, many kinds have more than two cotyledons, and are therefore
termed _polycotyledons_; again, the radicle usually adheres to the
albumen in which the embryo lies, hence they are sometimes named
_Synorhiza_. The veins of the leaves (in those whose leaves are
veined), are either simple or forked; in which respect they approach
the endogens on the one hand, and the acrogens on the other.
This concise definition of the natural divisions of the vegetable
kingdom will enable the reader to comprehend the botanical principles
which must guide him in his attempt to explore the ancient floras,
whose fossil remains are generally found in a very fragmentary
condition.
I need only add that M. Ad. Brongniart, in his great work on Fossil
Plants, arranges the vegetable kingdom into five classes, viz.:--
1. Cellular Cryptogamia,[36] or Amphigens.
2. Vascular Cryptogamia,[37] or Acrogens.
3. Monocotyledons.[38]
4. Gymnospermous Dicotyledons.[39]
5. Angiospermous Dicotyledons.[40]
[36] Plants having the fructification concealed, and of cellular
structure only.
[37] Plants having the fructification concealed, and with vessels, or
vascular tissue.
[38] Flowering plants with one cotyledon; the Endogens.
[39] Plants with naked seeds; that is, destitute of a pericarp or case.
[40] Plants with the seeds in a receptacle or pericarp, with a style
and stigma.
ON THE MODE OF INVESTIGATING FOSSIL REMAINS OF VEGETABLES.
[Sidenote: INVESTIGATION OF FOSSIL PLANTS.]
The distinguished authors of the British Fossil Flora justly remark,
that a few isolated, and very imperfect data, exclusively afforded by
the remains of the organs of vegetation, are but too often the sole
guide to the class, order, or genus of the fossil plants which the
geologist has to examine; hence, in most instances, a general idea
only can be obtained of the nature of the original.[41] To facilitate
the study of Fossil Botany they offer some practical suggestions,
which have served as the basis of the following directions for the
investigation of vegetable remains, and which the previous remarks
will, we trust, render intelligible.
[41] Foss. Flor. vol. I. p. xxvi.
1. _The Trunk, or Stem._--Examine if the wood in a transverse section
be disposed in concentric circles (as _Plate V. fig 4_): if so, it
belonged to an exogenous tree: if, on the contrary, the wood appears
deposited irregularly in spots (_Lign. 1, fig. 4_), then the original
was endogenous. If a transverse section show remains of sinuous,
unconnected layers, resembling arcs with their ends directed outwards,
and of a solid structure, and imbedded among looser tissue, then it
belonged to an arborescent fern; see the subjoined figures (_Lign. 2_).
[Illustration: Lign. 2. Sections of Fern-Stems.
Transverse sections (half the diameter) of two stems of recent
Arborescent Ferns, to show the zone of woody fibre disposed in arcs.
This structure is seen in the silicified trunks from Chemnitz.]
[Sidenote: INVESTIGATION OF FOSSIL STEMS.]
If the stem be in a state of preservation that will admit of the
slicing or chipping off a piece for microscopical investigation, the
process described at the conclusion of this section should be employed.
The following data may be thus obtained. If the structure be entirely
cellular, and it can be satisfactorily ascertained that it never
possessed vascular tissue, the original belonged to the _Cryptogamia_;
_i.e._ to fuci, mosses, and the like.
If it consist of parallel tubes, and has neither pith, nor rays
passing from the centre to the circumference, the tree or plant was
_endogenous_, like the Palm. If any trace be present of tissue crossing
the longitudinal tubes at right angles, and radiating from the centre
to the circumference, this will prove the existence of medullary rays,
and the original must have been _exogenous_, as the Oak, Elm, &c.: and
if in a transverse section the tubes appear of equal size, the tree was
probably _coniferous_, or _cycadeous_ (_i.e._ related to the plants
called _Cycas_ and _Zamia_); but if larger tubes appear among the
smaller ones, disposed in a definite manner (see _Plate V. fig. 4_),
it belonged to some other tribe of exogenous plants.
If the walls of the tubes be studded with glands (_Lign. 1, fig. 1,
c_; _Plate V. figs. 2^b 3^b_.); the fossil belongs to the Coniferæ.
If any vestige of a central pith be discovered, the exogenous nature of
the original is undoubted, for no other class, as we previously stated,
possesses a central cellular column.
The absence or presence of a true cortical investment, or bark, is
important, for a distinct bark is the characteristic of the _exogenous_
class:[42] a cortical integument, or rind, not separable from the
enclosed structure, indicates the _monocotyledons_; and the entire
absence of any rind, the _cryptogamia_.
[42] An apparent exception to this rule is found in the fossil genus
Clathraria, described hereafter, which has a distinct hollow cortical
cylinder, that separates from the internal axis: this is not true bark,
but is formed by the consolidation of the bases of the petioles or
leaf-stalks; see _Lign. 54_.
The markings on the stems, occasioned by the scars or cicatrices left
by the separation of the petioles or leaf-stalks (as on the stalk of a
cabbage), afford important evidence, since they are commonly present,
even when the cylindrical trunk is compressed into a flat thin layer of
coal; as we shall often have occasion to remark. In this place it need
only be stated, that by these scars may be detected the position of the
leaves, and the form of the bases of the petioles or leaf-stalks; their
probable direction, whether they were opposite, alternate, verticillate
or spirally disposed, deciduous or persistent, imbricated or remote.
Even when no traces of the leaves remain, the origin of the branches,
and their bifurcation, may perhaps be determinable.
2. _The Leaves._--In a fossil state the texture and surface of the
leaves are sometimes preserved; but in general the outline of the leaf,
its division and arrangement, and its mode of venation, can alone be
ascertained. The _venation_, that is, the form and distribution of the
vascular tissue, or vessels, through the leaf, is the most important
character for our guidance; and Dr. Lindley offers the following
suggestions on this point. If the veins be all parallel, not branched,
or only connected by little transverse bars, and the leaves undivided
(as in the Lily or Hyacinth), the plant was probably endogenous; but
if the leaf be divided or pinnated, it may be referable to Cycadeæ
(_Lign. 45_).
Leaves having the veins of equal, or nearly equal thickness, and
dichotomous (_forked_), or very fine, and simply divided, belong to the
fern tribe; to this division an immense proportion of the foliage found
in the carboniferous strata is referable; the genera of fossil ferns
have been constructed principally from the venation.
If the veins of a leaf be obviously of unequal thickness, and
reticulated, or disposed in net-like meshes, as in the rose and apple,
the original was dicotyledonous (_Plate III, figs. 4, 8_).
Leaves of a large size, destitute of veins, and irregularly divided,
probably belong to fuci, or other marine plants (_Lign. 10_).
Such are the rules for the investigation and interpretation of
the characters of stems and foliage, which have been preserved by
mineralization. Their application is not difficult, and the student may
by their assistance obtain some general indications as to the nature of
the original trees or plants, whose petrified remains form the subject
of his examination.
ON THE MICROSCOPICAL EXAMINATION OF FOSSIL VEGETABLES.
[Sidenote: MICROSCOPICAL EXAMINATION.]
Mr. Nicol, who first suggested the method now generally adopted for
preparing fossil wood, coal, &c. for microscopical examination, and
which was employed by Mr. Witham in the illustrations of his beautiful
work on the structure of fossil plants,[43] has so clearly explained
the process, that by a little practice the student will be able to
prepare specimens sufficiently thin for every useful purpose. Several
lapidaries in London, (see list at the end of this work,) polish and
mount fossil vegetables and other substances, in a very superior
manner; but their charges are high, and they frequently injure
specimens by grinding them too thin, and thus obliterating structure.
I would recommend that a small chip of the specimen, if possible in
a _radial_ direction, should be examined by reflected light, always
beginning with the lowest object-glass and eye-piece, and ascending to
the highest power; at first without any preparation;[44] subsequently
the object should be immersed in oil of turpentine, which will render
it somewhat transparent, and it then should be examined by transmitted
light. By this exploration we may detect structure, and ascertain if
the specimen be worth the trouble or expense of further preparation.
[43] Observations on Fossil Vegetables. 4to. 1833.
[44] The drawings in _Plate V. figs. 2 and 3_, of fossil coniferous
wood, were from chips seen by reflected light, and without any
preparation.
Coal may be prepared for examination, by removing with a sharp knife
a thin pellicle, or a minute scraping; immerse it in a drop of oil
of turpentine on a piece of glass; then add a little Canada balsam,
and hold the glass over the flame of a lamp till the balsam is spread
evenly over the specimen. But without any preparation, the surface of
coal recently broken may be successfully investigated. One of the most
interesting examples of coniferous structure in coal that my cabinet
contains, was discovered by my son in a piece lying on the fire, which
had been cracked by the heat; and I have another fragment, showing
the spiral vessels, and coniferous glands, which the Rev. J. B. Reade
obtained under similar circumstances. But for choice specimens, the
following method is to be employed; and in many cases no other plan
will succeed. Sections of teeth, bone, marble, &c. may be prepared by a
like process.
MODE OF PREPARING SLICES OF FOSSIL WOOD FOR MICROSCOPICAL EXAMINATION.
"Let a thin slice be cut off from the fossil wood, in a direction
perpendicular to the length of its fibres--the slice thus obtained must
be ground perfectly flat, and polished. The polished surface is then to
be cemented to a piece of plate glass (3 in. long and 1 in. wide) by
Canada balsam--a thin layer of balsam must be applied to the polished
surface of the slice, and also to one side of the glass--the slice and
the glass are now to be laid on any thin plate of metal, and gradually
heated over a slow fire, or a spirit lamp, to concentrate the balsam.
The heat must not be so great as to throw the balsam into a state of
ebullition; for if air bubbles be formed, it is difficult to get rid
of them, and if not removed they will prevent the complete adhesion
of the two surfaces when applied to each other; the heat of the metal
should never be so great that the fingers may not be held in contact
with it for a few seconds without inconvenience. When air bubbles are
formed, they should be displaced by a small piece of wood tapering to
a point; when the balsam is thought to be sufficiently concentrated,
and all the air bubbles have disappeared, the slice and glass may be
taken from the heated metal, and pressed closely together; a slight
degree of pressure will suffice to expel the super-abundant balsam, and
this will be facilitated by gently sliding the specimen to and fro on
the glass; by this kind of motion any air that may have got entangled
when the two surfaces were brought in contact, will also be removed.
When the whole is cooled down to the temperature of the air, and the
balsam has become solid, that part which adheres to the surface of the
glass surrounding the slice should be scraped off with the point of a
penknife; and by this operation, it will at once be seen whether the
balsam has undergone the requisite concentration; for if it flakes off
before the knife, it will be found that the slice and glass will cohere
so firmly, that in the subsequent grinding, there will be no risk
of their separating from each other; but if the balsam has not been
sufficiently concentrated, it will slide before the knife, and in that
case the two bodies will not adhere with requisite firmness. If the
layer of balsam applied to the two surfaces be not too thick, its due
concentration will be accomplished in four or five minutes, provided
the application of the heat be properly regulated. The slice must now
be ground to that degree of thinness which will permit its structure
to be seen by the help of a microscope. This will be accomplished by
rubbing the slice, by a rapid circular motion with the hand, on a piece
of sheet lead, supplied with a little emery (_size_ No. 1.) moistened
with water; when the emery ceases to act, the muddy matter remaining
should be removed, and a fresh portion of emery applied; this must be
repeated until the surface of the slice is perfectly flat; a sheet of
copper must then be substituted for the lead, and the fossil ground as
smooth as possible by flower of emery, freed from its coarser parts.
The surface may then be polished by friction, with _crocus_ or rotten
stone, on a transverse section of any soft wood."[45]
[45] Mr. Witham, Observations on Fossil Vegetables.
CHAPTER V.
ON PEAT-WOOD, LIGNITE, AND COAL.
[Illustration: Lign. 3. Nodule of Ironstone inclosing a Fern-leaf.
_Coalbrook Dale._
Fig. 1.--The nodule in its natural state.
2, 3.--The same, split open longitudinally. The leaf
remains attached to fig. 2, and the impression
of its upper surface is seen on fig. 3.
4.--Outline of the form of the leaf, which is a species
of Pecopteris.
]
[Sidenote: PEAT-WOOD, LIGNITE, AND COAL.]
Before entering upon the examination of the specific and generic
characters of fossil plants, and the natural relations of the extinct
forms with those of the existing Floras, it will be requisite to
notice those vast beds of vegetable matter, in various states of
carbonization, which occur in the palæozoic, secondary, and tertiary
formations.
Submerged Forests. Peat.--The phenomenon of extensive tracts of
marsh-land, with layers of prostrate trees of all ages, lying but a
few feet beneath the common alluvial soil, is of frequent occurrence,
both inland, and in many places along the shores of our island. (_Geol.
S. E._ p. 18). These submerged forests are generally situated below
the level of the sea, and afford unquestionable proof of subsidences
of the land. The trees are of the kinds indigenous to the districts
in which they occur; and leaves and seeds of the hazel, beech, elm,
&c. are often preserved in the silt in which the prostrate forests are
imbedded. On the Sussex coast there are accumulations of this kind, at
Bexhill, Pevensey levels, Felpham, &c.
The extensive subterranean forests exposed in the Fens of Lincolnshire
by the operations carried on for draining that district, must be
familiar to those who travel by the Great Northern Railway: the
protruding upright stems, broken off at a short distance above the
primitive soil, will remind the geological observer of the petrified
forest of the Isle of Portland.
The wood in these cases has undergone no change but that of being dyed
black, by an impregnation of solutions of iron; and many trunks are
in so sound a state as to be employed in building. The oak timbers of
the Royal George, lately raised up from off Portsmouth, after being
immersed in silt about sixty years, closely resemble in colour and
texture the wood of the submerged forests. Skeletons of deer, horse,
swine, &c. are occasionally found imbedded in these subterranean
accumulations of vegetable remains; and sometimes canoes, formed of the
trunk of an oak, constructed by the aboriginal inhabitants of Britain,
with stone implements called celts, are met with at considerable depths.
In the peat-bogs of Ireland (_Wond._ p. 66), large forest trees often
occur, together with the skeletons of the elk, deer, and other animals
of the chase; and in a few instances the bodies of the primitive
hunters, wrapped in skins, have been discovered.
In Belfast Lough, a bed of peat is situated beneath the ordinary level
of the waters, but is generally left bare at the ebb tides. Trunks and
branches of trees, with vast quantities of hazel nuts, are imbedded in
the peat; the whole being covered by layers of sand, and blue clay, or
silt. In most cases the pericarps of the nuts are empty, the kernels
having perished; but on the eastern side of the Lough, which is bounded
by limestone rocks, they contain calc-spar, which in some examples
forms a lining of delicate crystals (_Plate V. fig. 6_); while in
others the kernel is transmuted into calcareous spar (see _Plate III.
fig. 7_); but the pericarps are unchanged, and in the state of common
dried nut-shells; the water which deposited the spar in their cavities
not having left a particle of mineral matter in the ligneous substance
through which it had filtrated.
In a subterranean forest at Ferry-bridge, Yorkshire, hazel nuts in a
similar mineralized state occur, and the branches and stems of the
trees have undergone a like change; the central ligneous axis is
petrified, while the outer zones have undergone no lapidification, but
remain in the state of dry rotten wood.[46]
[46] Specimens are preserved in the Museum at York.
[Sidenote: PEAT.--LIGNITE.--BROWN COAL.]
Lignite, Brown Coal, or Cannel Coal; these are terms employed to
designate certain varieties of carbonized wood, in which the ligneous
structure is more or less distinctly preserved. Lignite may be regarded
as an imperfect coal, for in its chemical properties it holds an
intermediate place between peat and bituminous coal. It is for the most
part found in tertiary formations, but is not unfrequent in ancient
secondary deposits, and may occur in the earliest sedimentary rocks
which contain vegetable remains.
The newer deposits of _Brown or wood-coal_, are commonly situated in
depressions or basins, as if they had been produced by the submergence
of woods and forests, in a swamp or morass; and in many instances the
ligneous structure is distinct in one part of the bed, while in another
the mass is a pure black coal, differing in no respect from true coal,
except that it is less dense.
_Bovey Coal._--One of the most instructive deposits of brown coal in
England, is that of Bovey Heathfield, near Chudleigh in Devonshire,
which is of considerable thickness and extent, and presents all the
characters of a true coal-field; namely, beds of carbonized vegetables,
alternating with layers of clay and marl. The Bovey coal is in the
state of bituminized wood, the vascular tissue (which is coniferous in
the specimens that have come under my notice) being apparent. It is
easily chipped or split, and leaves a considerable quantity of white
ashes after combustion. The layers of coal vary in thickness from one
foot to three feet; and there are eighteen or twenty in a depth of
about 120 feet; this coal-field extends seven or eight miles. No leaves
or fruits have been discovered; bitumen occurs both in the coal and
in the intermediate clays. Calcareous spar, and iron pyrites, prevail
in many of the strata. In some places this brown coal is covered by a
bed of peat, in which trunks and cones of firs are imbedded. The whole
series appears to have been a lacustrine deposit; probably formed in a
lake, into whose basin rafts of pine forests were drifted by periodical
land-floods. (Org. Rem. I. p. 327).
The brown-coal formations on the banks of the Rhine, present the same
phenomena on a more extended scale, and complicated with changes
induced by volcanic action. In Iceland, where at the present time
forests are unknown, there are extensive deposits of lignite of a
peculiar kind, termed _surturbrand_.
[Sidenote: JET.--WEALDEN COAL.]
_Jet._--The beautiful substance called Jet, is a compact lignite,
and the vascular tissue may be detected even in the most solid
masses; when prepared in very thin slices, it appears of a rich brown
colour by transmitted light, and the woody texture is visible to the
naked eye. Jet is found in great purity and abundance in the cliffs
of alum-shale on the Yorkshire coast, which were celebrated in the
early centuries for the production of this substance. At Whitby and
Scarborough extensive manufactories of ornaments and trinkets of jet
are established. The sandstone cliffs near Whitby contain masses of a
very compact variety, locally termed stone-jet. In the front of the
cliff, on the north-west side of Haiburn Wyke, the stump of a tree
was observed in an erect position, about three feet high, and fifteen
inches in diameter; the roots traversed a bed of shale, and were in the
state of coarse jet, but the trunk, which extended into the sandstone,
was in part silicified, while other portions were decayed and had a
sooty aspect.[47]
[47] Geological Survey of the Yorkshire Coast; by Rev. G. Young; 1828;
p. 197.
Thin seams and layers, and nodular masses, as well as regular
coal-fields of lignite, occur in the tertiary formations. At Castle
Hill, near Newhaven, in Sussex (_Wond._ p. 239), a seam of lignite
resembling the surturbrand of Iceland, a few inches thick, is
interposed between strata of red marl in which are carbonized leaves of
dicotyledonous trees.
At Alum Bay in the Isle of Wight, a layer of lignite occurs between the
beds of vertical gravel and sand of that interesting locality.
Wealden Coal.--The Wealden formation, in some districts, contains
layers of lignite, which alternate with finely laminated micaceous
sandstones, marls, and clays, abounding in minute carbonized
fragments of fern-leaves, with fresh-water shells, and entomostracous
crustaceans. This series of strata so strikingly resembles in its
general aspect the characters of a coal-field, that some years since
extensive works were undertaken in Sussex, in the expectation that
coal might be obtained of suitable quality for economical purposes.
The search was unsuccessful, but the attempt deserves not the censure
that was bestowed upon it, in the infancy of geological science;[48]
for experience has since shown, that although the true coal-measures
are only found beneath the Triassic and Permian formations, good
combustible bituminous coal is not necessarily restricted to any period
or series of strata, but may occur wherever the local conditions
were favourable to the accumulation and bituminization of vegetable
matter. In fact, the coal-fields of the north of Germany are of the
Wealden epoch; and this coal more closely approaches in its chemical
characters the black-coal of the ancient carboniferous formations,
than any of the lignites and brown-coals of the tertiary strata. Some
of the beds are highly bituminous, especially those of Schaumberg,
and of the principality of Bückeburg, which may rank with the best
English Newcastle coal; but those layers which are derived from
coniferous trees and plants are more laminated, and somewhat resemble
the brown-coal. These deposits have originated for the most part from
carbonized conifers and cycads, with a few ferns and lycopodiaceæ, or
club-mosses.
[48] See Sir J. F. W. Herschel's Discourse on Nat. Phil.
The brown-coal of Hohen-Warte by the Osterweld, is chiefly formed
of the _Abies Linkii_, and _Pterophyllum Lyellianum_, whose leaves
and twigs, closely impacted together, are generally of a brownish
colour, have a glossy surface, and, when soaked in water, are
perfectly flexible. The other modification of Wealden coal appears to
have undergone a greater degree of pressure, and of exclusion from
the atmosphere; no ligneous structure is apparent, but indistinct
impressions of leaves are perceptible, and these are chiefly of ferns
and club-mosses. This coal has probably resulted from an accumulation
of plants of less firm texture, and more perishable, than those of
which the former is composed.[49]
[49] See Dr. Bunker's Mon. Norddeutsch. Weald.
Many interesting facts relating to the carbonization of vegetables,
came under my observation during my researches in the Wealden strata;
and it is a subject of regret to me, that circumstances prevented my
following up the investigation of those still imperfectly explored
deposits. Small nodular portions of coal, in which no structure is
apparent, often occur in the calciferous grit of Tilgate Forest; and
sometimes large masses of lignite, fissured in every direction, and
having the interstices filled with white calcareous spar.[50] Some of
the sandstones are discoloured by the abundance of minute particles
of lignite, produced by the disintegration of ferns peculiar to the
country of the Iguanodon.
[50] A fine specimen of this kind is in the British Museum.
The original structure and composition of a plant doubtless affected
its carbonization; for in the same layer of stone, the stems of
Endogenites, hereafter described, invariably possess a thick, outer
crust, of coal; while those of Clathrariæ, plants allied to the Cycads,
have not a particle of carbonaceous matter, but are surrounded by a
reddish brown earthy substance. The nature of the stratum in which
the plants were imbedded, must also have influenced the process
of bituminization. Masses of vegetables buried beneath beds of
tenacious clay, by which the escape of the gaseous elements set free
by decomposition was prevented, must have been placed under the most
favourable conditions for their conversion into lignite and coal.
That the production of lignite is still going on there can be
no doubt; and the following instance of a bed of recent origin,
affords an instructive illustration of the subject. Near Limerick,
in the district of Maine, one of the States of North America,
there are peat-bogs of considerable extent, in which a substance
similar to cannel-coal is found at the depth of three or four feet
from the surface, amidst the remains of rotten logs of wood, and
_beaver-sticks_:[51] the peat is twenty feet thick, and rests upon
white sand. This coal was discovered on digging a ditch to drain a
portion of the bog, for the purpose of obtaining peat for manure. The
substance is a true bituminous coal, containing more bitumen than is
found in any other variety,[AZ] Polished sections of the compact masses
exhibit the peculiar structure of coniferous trees, and prove that the
coal was derived from a species allied to the American fir.
[51] Pieces of wood fashioned by the beavers for the construction of
their dams.
[52] An analysis of 100 grains gave the following results:--Bitumen 72;
carbon, 21; oxide of iron, 4; silica, 1; oxide of manganese, 2; = 100.
[Sidenote: COAL.]
Coal.--We proceed to the examination of that remarkable substance which
has resulted from the perfect bituminization of the vegetables of the
most ancient Flora which geological researches have brought to light,
and to which the term _Coal_ is commonly restricted.
Although Balthazar Klein in the sixteenth century affirmed that coal
owed its formation to wood and other vegetable substances,[53] yet I
can well remember when many eminent geologists were sceptical on this
point; and the truth in this, as in most other questions of natural
philosophy, was established with difficulty. The experiments and
observations of the late Dr. Macculloch, mainly contributed to solve
the problem as to the vegetable nature of this substance; and that
eminent chemist and geologist successfully traced the transition of
vegetable matter from peat-wood, brown-coal, lignite, and jet, to
coal, anthracite, graphite, and plumbago. Nor must the meritorious
labours of that accomplished naturalist, and excellent man, the late
Mr. Parkinson, author of the "_Organic Remains of a Former World_,"
in this field of research, be forgotten.[54] The first volume of that
work, which treats on fossil plants, contains much original information
on the transmutation of vegetables into the various mineral substances
in which the nature and original structure of the originals are
altogether changed and obliterated; it may still be consulted by the
student with advantage.
[53] Sternberg's "Flore du Monde Primitif."
[54] See my "Pictorial Atlas of Organic Remains," 1850.
Although the vegetable origin of all coal will not admit of question,
yet evidence of the internal organization of the plants of which it
is composed, is not always attainable; for the most perfect coal
has undergone a complete liquefaction, and if any portions of the
structure remain, they appear under the microscope as if imbedded in
a pure bituminous mass. The slaty coal generally preserves traces of
cellular or vascular tissue, and the spiral vessels, and the dotted
cells of coniferous trees, may readily be detected in chips or slices,
prepared in the manner previously pointed out (_ante_, p. 66). In
many examples the cells are filled with an amber-coloured resinous
substance; in others the organization is so well preserved, that on
the exposed surface of a piece of coal cracked by exposure to heat,
the vascular tissue, spiral vessels, and cells studded with glands,
may be detected. Even in the white ashes left after combustion, traces
of the spiral vessels are often discernible under a highly magnifying
powder. Some beds of coal are wholly composed of minute leaves and
disintegrated foliage; and if a mass recently extracted from the mine
be split asunder, the surface is seen to be covered with flexible
pellicles of carbonized leaves and fibres, matted together; and flake
after flake may be peeled off through a thickness of many inches,
and the same structure be apparent. Rarely are any large trunks or
branches observable in the coal; the appearance of many beds being that
of a deposit of foliage, shed and accumulated in a forest, (as may be
observable in existing pine-districts,) and consolidated by pressure,
while undergoing that peculiar change by which vegetable matter is
converted into a carbonaceous mass.
In fine, a gradual transition may be traced from the peat-wood and
submerged forests of modern times, in which leaves, fruits, and trunks
of indigenous trees and plants are preserved, to those vast deposits of
mineral coal, formed by the bituminization of the extinct Floras which
flourished in the palæozoic ages.
The geological position of the ancient coal, the manner in which it
is interstratified with layers of clay, shale, micaceous sandstone,
grit, and ironstone--in some districts associated with beds of
fresh-water shells (_Sil. Syst._ p. 84)--in others alternating with
strata containing marine remains,--are fully treated of in _Wond._
pp. 729-733, and _Bd._ p. 525; and it is not within the scope of the
present work to dwell in detail upon what may be termed the physical
geology of the carboniferous deposits. But a few observations on the
phenomena presented by these accumulations of bituminized vegetables
and their associated strata, are necessary to render the subsequent
remarks on the habits and affinities of the plants composing the
palæozoic Flora intelligible to the general reader.
While the essential conditions for the conversion of vegetable
substances into coal appear to be the imbedding of large quantities
of recent trees and plants in a deposit which shall exclude the air,
and prevent the escape of the gaseous elements when released by
decomposition from their organic combination, so, according to the
more or less perfect manner in which these conditions are fulfilled,
will result coal, jet, lignite, brown-coal, or peat-wood; or a mass of
partially carbonized vegetables, like that observable when new-mown
hay undergoes spontaneous combustion, from bituminous fermentation in
the atmosphere (_Wond._ p. 701. _Org. Rem._ I. p. 181).
The manner in which the carboniferous strata have been deposited, has
been a subject of much discussion. Some contend that the coal-measures
were originally in the state of peat-bogs, and that the successive
layers were formed by the subsidences of forests which grew on the
sites now occupied by their carbonized remains; others suppose
that the vegetable matter originated from rafts, like those of the
Mississippi, which floated out to sea, and became engulfed; while
many affirm that the coal-measures were accumulated in inland seas
or lakes, the successive beds of vegetable matter being supplied by
periodical land-floods; and the supporters of each hypothesis bring
numerous facts in corroboration of their respective opinions. There
can, I think, be no doubt that the production of coal has taken place
under each of these conditions, and that at different periods, and in
various localities, all these causes have been in operation; in some
instances singly, in others in combination. Coal may have been formed
at the bottom of fresh-water lakes, as in those instances where it is
associated with fresh-water shells and crustaceans, as at Burdie House
(_Wond._ p. 693), and in some of the Derbyshire and Yorkshire deposits;
in the beds of rivers and estuaries, as in the Wealden, and in the
Shrewsbury coal-field;[55] and from drifted forests, like the rafts
of the American rivers, transported into the sea, and engulfed in the
abyss of the ocean;[56] and the remains of terrestrial, lacustrine,
and marine animals, may accordingly be found associated with it.[BE]
But though many coal-fields (or basins, as they are termed, because
they occupy depressions) have evidently been produced by different, and
local agencies, the sedimentary deposits and coal-beds comprised in the
carboniferous formations, setting aside unimportant variations, present
a remarkable uniformity of character in their nature and arrangement,
not only throughout Great Britain and Europe, but in every other part
of the known world.
[55] In this coal-field are beds of limestone several feet thick,
abounding in cyprides, fresh-water mollusks, &c.--_Sil. Syst._ p, 84.
[56] The immense thicknesss of some coal-beds, without any
intercalations of earthy materials, seems to be inexplicable on any
other supposition but that of accumulations of drift-wood and plants.
In the Great Exhibition of 1851, there was exhibited, on the outside of
the west end of the Crystal Palace, a section of the lowest bed of coal
from Tividale Colliery in South Staffordshire, the total thickness of
which was 29 feet, with no intermixture whatever of sediment, except
some thin shaly partings: the entire mass was composed of carbonized
vegetables.
[57] Sir R. I. Murchison has treated this subject with great ability:
see _Sil. Syst._ chap, xi., and the illustrative maps opposite, p. 152.
[Sidenote: STRATIFICATION OF A COAL-FIELD.]
Stratification of a Coal-field.--The group of strata constituting a
coal-field consists of an alternation of layers of coal and of clay,
of variable thickness, resting, very generally, on grit, or marine
limestone abounding in shells, corals, and crinoidea.
My late excellent friend, Mr. Bakewell, used to exemplify the
manner in which the beds of coal are interstratified with layers of
clay and shale, by the following apt illustration; let a series of
mussel-shells be placed one within the other, and a layer of clay be
interposed between each; the shells will represent the beds of coal,
and the partitions of clay the earthy strata intercalated between the
carboniferous layers; now, if one side of the series of shells be
raised to indicate the general rise of the strata in that direction,
and the whole be dislocated by partial cracks and fissures, the general
arrangement and subsequent displacement of the beds will be represented.
The principal feature which arrests attention on the examination of
the section of a coal-pit, is the uniform presence of a thick bed
of clay beneath every layer of coal; but a still more extraordinary
fact remains to be mentioned, namely, that a common plant of the
coal strata, called Stigmaria, (hereafter described, see _Lign.
36, 38_,) invariably occurs, more or less abundantly, in this bed of
under-day, although very rarely to be met with in the coal or shale
above. This phenomenon, long since noticed by Martin, Macculloch, and
other authors, but whose value was not duly estimated till the recent
observations of Mr. Logan, (_Geol. Proc._ vol. iii. p. 275,) is also
found to prevail throughout the Welsh coal formation, which is upwards
of twelve thousand feet in thickness, and contains more than sixty
beds of coal, and as many of clay with stigmariæ; the Appalachian
coal-measures of the United States present the same characters.[58] To
place this fact before the student in a clear point of view, I will
describe one of the triple series of beds which compose a coal-field.
[58] See Prof. Rogers, in the Proceedings of the American Geologists,
p. 453; and Sir C. Lyell's Travels in America.
1. _Under-clay_; the lowermost stratum. A tough argillaceous substance,
which upon drying becomes a grey friable earth: it is occasionally
black, from the presence of carbonaceous matter. It contains
innumerable stems of stigmariæ, which are generally of considerable
length, and have their rootlets or fibres (see _Lign. 38_) attached,
and extending in every direction through the clay: these stems commonly
lie parallel with the planes of the bed, and nearer to the top than to
the bottom.
2. _Coal._ A carbonized mass, in which the external forms of the plants
and trees composing it are obliterated, but the internal structure
remains; large trunks or stems, and leaves, are rarely distinguishable
in it, but the presence of coniferous wood in many beds of coal, proves
that this arises, not from the absence of trees, but from their
external forms having been obliterated.
3. _The Roof_, or upper bed. This generally consists of slaty clay,
abounding in leaves, trunks, stems, branches, and fruits, and
contains layers and nodules of ironstone, inclosing leaves, insects,
crustaceans, &c.
In some localities beds of fresh-water mussels, and in others of marine
shells, are intercalated; layers of shale, finely laminated clay,
micaceous sand and grit, and pebbles of limestone, granite, sandstone,
and other rocks, are often present. The most illustrative examples
of the foliage of the carboniferous flora are found in this deposit,
which appears to be an accumulation of drifted materials derived from
other rocks, and promiscuously intermingled with the dense foliage and
stems of a prostrate forest; the whole having been transported from a
distance by a powerful current or flood.
[Sidenote: ORIGIN AND NATURE OF COAL.]
Thus we have, in the first place, spread uniformly over the bottom,
and constituting the bed on which the coal reposes, a stratum of clay
(_Under-clay_), composed of fine pulverulent materials, which may have
once constituted the soil of a vast plain or savannah; the only remains
found in it are the roots of gigantic trees (see _Lign. 36_); for such
the stigmariæ are now proved to have been, and not aquatic plants, as
was formerly supposed (_Bd._ p. 476).
Secondly, a bituminous mass (Coal), composed of coniferous wood,
gigantic ferns, club-mosses, &c.; occasionally with trunks of trees
penetrating vertically through it.
Thirdly, a deposit of drift or water-worn materials (_the Roof_), mixed
with the foliage and stems of numerous species of terrestrial plants;
the whole appearing to have been subjected to the action of currents.
The first, or _Under-clay_, may have been the natural soil, in which
the stigmariæ grew; the next,--the _Coal_,--the carbonized stems, and
other remains of the trees to which the roots belonged: and the last,
or uppermost, forming the roof of the coal, may have resulted from
the foliage and branches of a prostrate forest, overwhelmed and buried
beneath the transported detritus of distant rocks.
These phenomena may be explained by supposing the inundation of a
thickly-wooded plain from an irruption of the sea; or of a vast
inland lake, occasioned by the sudden removal of some barrier; or
by a subsidence of the tract of country on which the forest grew.
But when we find an accumulation of strata, in which triple deposits
of this kind are repeated some thirty or forty times through a
thickness of many thousand feet, this solution of the problem is not
satisfactory. Not only subsidence after subsidence must have taken
place, but the first submergence have been followed by an elevation
of the land--another soil, fit for the growth of forest trees, must
have been produced--another generation of vegetables, of precisely the
same species and genera, have sprung up, and arrived at maturity--and
then another subsidence, and another accumulation of drift. And these
periodical oscillations in the relative level of the land and water
must have gone on uninterruptedly through a long period of time, not
in one district or country only, but in various parts of the world,
during the same geological epoch. At present I do not think we have
data sufficient to explain these phenomena; what has been advanced
may, perhaps, serve to elicit further information, by pointing out
the difficulties in which the question is involved, and showing
what interesting fields of discovery are still unexplored, and how
comprehensive and important are the objects that come within the scope
of geological investigation.[59]
[59] I would refer the student for a fuller consideration of the
phenomena thus briefly noticed, to the 6th edition of my Wonders of
Geology, pp. 669, 718, 731.
* * * * *
I will conclude this chapter with the following beautiful reflections
of Dr. Buckland on the origin and nature of Coal, and the changes it
undergoes when rendered subservient to the necessities and luxuries of
man.
"Few persons are aware of the remote and wonderful events in the
economy of our planet, and of the complicated applications of human
industry and science, which are involved in the production of the coal
that supplies with fuel the metropolis of England.
"The most early stage to which we can carry back its origin, was among
the swamps and forests of the primeval earth, where it flourished
in the form of gigantic Calamites, and stately _Lepidodendra_, and
_Sigillariæ_. From their native bed, these plants were transported
into some adjacent lake, or estuary, or sea. Here they floated on the
waters, until they sank saturated to the bottom, and being buried in
the detritus of adjacent lands, became transferred to a new estate
among the members of the mineral kingdom. A long interment followed,
during which a course of chemical changes, and new combinations of
their vegetable elements, converted them to the mineral condition of
coal. By the elevating force of subterranean agency, these beds of
coal have been uplifted from beneath the waters, to a new position in
the hills and mountains, where they are accessible to the industry of
man. From this fourth stage, coal has been removed by the labours of
the miner, assisted by the arts and sciences, that have co-operated to
produce the steam-engine, and the safety-lamp. Returned once more to
the light of day, and a second time committed to the waters, it has,
by the aid of navigation, been conveyed to the scene of its next and
most considerable change by fire; a change during which it becomes
subservient to the most important wants and conveniences of man. In
this seventh stage of its long eventful history, it seems, to the
vulgar eye, to undergo annihilation; its elements are, indeed, released
from the mineral combinations which they have maintained for ages, but
their apparent destruction is only the commencement of new successions
of change and of activity. Set free from their long imprisonment, they
return to their native atmosphere, from which they were absorbed by the
primeval vegetation of the earth. To-morrow they may contribute to the
substance of timber, in the trees of our existing forests; and having
for a while resumed their place in the living vegetable kingdom, may,
ere long, be applied a second time to the use and benefit of man. And
when decay or fire shall once more consign them to the earth, or to the
atmosphere, the same elements will enter on some further department of
their perpetual ministration in the economy of the material world."[60]
[60] Bd p. 481.
CHAPTER VI.
FOSSIL VEGETABLES.
In the present section of this work, I propose to explain the botanical
arrangement and nomenclature of fossil plants; and figure and describe
one or more species of the genera that are most likely to come
under the observation of the student, either in public or private
collections, or in the course of his researches in the field.
To determine the botanical relations of fossil leaves and stems,
reference must be had to works expressly devoted to the subject;
namely, the "_British Fossil Flora_," by Dr. Lindley and Mr. Hutton,
and the "_Histoire des Végétaux Fossiles_," by M. Adolphe Brongniart.
The classification of the last-named eminent botanist is here adopted,
as the most easy of application.
With regard to the nomenclature, it may be necessary to remark, that
when a fossil plant undoubtedly belongs to a recent genus, the usual
botanical name is employed: for example, _Equisetum Lyellii_; when the
fossil does not possess all the generic characters, yet is evidently
allied to a recent genus, the term _ites_ (from λιθος, _lithos_,
stone), is added--as _Equisetites_, _Palmacites_, &c.; and this
termination is invariably adopted by some authors. When the fossil
plant differs altogether from any known type, it is distinguished by
some arbitrary generic name, as _Bucklandia_, _Sigillaria_, &c.
There are also a few provisional genera for the reception of fossil
leaves, fruits, and stems, whose characters and relations are but
imperfectly known; as Carpolithes, Endogenites, &c. Upon these
principles the present arrangement has been founded: the progress of
discovery will, of course, be continually adding to the list, and the
classification require to be modified.
[Sidenote: FOSSIL CRYPTOGAMIA.]
The following account of the principal types of the ancient floras
whose relics are preserved in the mineral kingdom, though commencing
with those of the most simple structure, the _Cryptogamia_, and
advancing to the higher orders, is not strictly botanical; for it was
found convenient, in some instances, to notice certain species and
genera of different orders under the same head, from their occurrence
in the same geological formations.
It is estimated that not more than two thousand species of plants have
been discovered in a fossil state, while the known recent species
amount to upwards of eighty thousand.
Cellular Cryptogamia; Algæ.--The plants designated by botanists _Algæ_,
and commonly known as sea-weeds, lavers, and fresh-water mosses, are
of the most simple structure--mere aggregations of cells--but present
innumerable varieties of form and magnitude: many species are mere
vesicles of such minuteness as to be invisible to the unassisted eye,
except accumulated in countless myriads, when they appear as a green,
purple, or reddish, slime in the water; or as a film on wood or stone,
or on the ground, in damp situations; while others are tough branched
marine plants, many fathoms in length.
The Algæ form three principal groups: 1. the _jointless_, as the
Fuci, the Dulses, Tangles, and Lavers: 2. the _jointed_, which are
composed of thread-like articulated tubes; such are the fresh-water
Confervæ: 3. the _disjointed_, or Brittle-worts, so called from their
spontaneous self-division, which is in some kinds complete, in others
only partial; and these, by separating transversely, and leaving
each cell or frustule attached at the angles, produce those beautiful
chains of angular green transparent cases, so constantly seen under
the microscope when substances from fresh-water streams or lakes are
submitted to examination.
As many of these forms are endowed with spontaneous motion, and possess
other properties common to animal organization, it is not surprising
that their vegetable nature was doubted, and that even so profound
a naturalist as M. Ehrenberg placed them in the animal kingdom:
the greater number being comprised in his family of _Bacillariæ_,
were described in the former edition of this work, as Infusoria or
Animalcules; in conformity with the classification of the illustrious
microscopist, whose splendid works and indefatigable labours have so
greatly promoted the advancement of microscopical investigation.[61]
[61] The whole of the objects called _Infusoria_ in the first edition
of "The Medals of Creation" belong to various kinds of Diatomaceæ.
[Sidenote: FOSSIL DIATOMACEÆ.]
These minute vegetable organisms are placed by botanists in two
tribes, the _Diatomaceæ_ or the _Brittle-worts_, and the _Desmidieæ_.
The latter are exclusively inhabitants of fresh-water, while a large
proportion of the former are marine plants. Some naturalists (M.
Brébisson) restrict the name _Diatomaceæ_ to those species which
secrete siliceous envelopes; and that of _Desmidieæ_ to those whose
structures are not siliceous, and are reducible by heat to carbon. As
the durable parts of these plants alone concern the geologist, the name
_Diatomaceæ_ will be employed as a general term in reference to their
fossil remains.
These tribes of Algæ abound in every lake and stream of fresh-water,
in every pool or bay, and throughout the ocean from the equator to
the poles. Certain kinds of sea-weeds secrete carbonate of lime; but
the Diatomaceæ have the power of separating silex, or the earth of
flint, from the water, by some unknown process, and their tissues are
composed of pure quartz: hence, under the microscope, their remains,
consisting wholly of rock crystal, exhibit the most exquisite forms,
elaborately fretted and ornamented (see _Lign. 4_). After the death and
decomposition of these plants, their durable frustules or cases appear
as colourless discs, cups, spheres, shields, &c., and these accumulate
at the bottom of the water in such inconceivable numbers, as to form
strata of great thickness and extent. Slowly, imperceptibly, and
incessantly, are the vital energies of these atoms separating from the
element in which they live the most refractory and enduring of mineral
substances, silex, and elaborating it into imperishable structures, and
thus adding enormous contributions to the accumulations of detritus,
which make up the sedimentary rocks of the crust of the globe.
The extent of this infinitesimal flora throughout regions where no
other forms of vegetation are known, is strikingly demonstrated by the
observations of our eminent botanical traveller. Dr. Joseph Hooker, in
his account of the Antarctic regions.[62]
[62] "On the Botany of the South Polar Regions;" in Sir J. Ross's
Voyage of Discovery.
"Everywhere," Dr. Hooker states, "the waters and the ice alike abound
in these microscopic vegetables. Though too small to be visible to
the unassisted eye, their aggregated masses stained the iceberg and
pack-ice wherever the latter were washed by the sea, and imparted a
pale ochreous colour to the ice. From the south of the belt of ice
which encircles the globe, to the highest latitudes reached by man,
this vegetation is everywhere conspicuous, from the contrast between
its colour and that of the white snow and ice in which it is imbedded.
"In the 80° of south latitude all the surface ice carried along by
currents, and the sides of every berg, and the base of the great
Victoria barrier itself--a perpendicular wall of ice, from one to two
hundred feet above the sea level--were tinged brown from this cause, as
if the waters were charged with oxide of iron. The majority of these
plants consist of simple vegetable cells enclosed in indestructible
silex; and it is obvious that the death of such multitudes must form
sedimentary deposits of immense extent.
"The universal existence of such an invisible vegetation as that of the
Antarctic Ocean is a truly wonderful fact, and the more so from its
being unaccompanied by plants of a high order. This ocean swarms with
mollusca, and entomostracous crustaceans, small whales, and porpoises;
and the sea with penguins and seals, and the air with birds; the animal
kingdom is everywhere present, the larger creatures preying on the
smaller, and these again on those more minute; all living nature seems
to be carnivorous. This microscopic vegetation is the sole nutrition
of the herbivorous animals; and it may likewise serve to purify the
atmosphere, and thus execute in the Antarctic latitudes the office of
the trees and grasses of the temperate regions, and the broad foliage
of the palms of the tropics."
Dr. Hooker also remarks that the siliceous envelopes of the same kinds
of diatomaceæ now living in the waters of the South Polar Ocean, have
contributed in past ages to the formation of European strata; for the
tripoli and the phonolite stones of the Rhine, contain the siliceous
envelopes of identical species.
Such are the comments of one of our most distinguished botanists, on
the phenomena under review. The reader will perhaps ask, what then are
the essential characters which separate the animal from the vegetable
kingdom? To this question it is impossible to give a satisfactory
reply: perhaps the only distinction that will be generally admitted by
zoologists and botanists is the following:--_animals require organic
substances for their support; vegetables derive their sustenance from
inorganic matter_.
[Sidenote: RECENT DIATOMACEÆ.]
Recent Diatomaceæ. _Plate IV._--To familiarize the reader with
the nature of these vegetable organisms, a few recent species are
represented in Plate IV., coloured as they appear when alive, under the
microscope; the figures are magnified as expressed by the fractions.
_Xanthidium._ _Plate IV. figs. 1, 2, 3, 4, 5._--The case or frustule
of this genus consists of a hollow, siliceous globe, beset with
spines. The increase of the Xanthidia by self-division, produces the
double appearance in the figures, all of which are in the progress of
separation.[63]
[63] The organisms so abundant in the flint and chalk, and which were
referred by M. Ehrenberg to this genus, and consequently described
under the name of Xanthidia by myself and others, are certainly in
nowise related to the recent forms: they are flexible envelopes, and
probably belong to zoophytes; as will be shown in the sequel.
_Pyxidiculum._ _Plate IV. fig. 2._--The case is a little saucer-shaped
box, and is invested by a membrane.
_Bacillaria._ _Plate IV. fig. 6._--A simple siliceous frustule, of a
prismatic shape, forming a brilliant chain, which often appears in
zigzag, in consequence of incomplete self-division. An immense number
and variety of forms are placed in this family by Ehrenberg, with
a multitude of generic and specific names. The fresh-water species
inhabit every pond and lake, and the marine every sea. Fossil species
are equally abundant.
_Cocconeis._ _Plate IV. fig. 7._--This is a very elegant type; the
frustule consists of a simple siliceous case, with a central opening;
it never occurs in chains like the former. It has been found fossil
near Cassel.
_Navicula._ _Plate IV. figs. 8, 9, 14, 15._--The plants of this genus
are free, and float in the water apparently by the agency of cilia.
Their case is a boat-like envelope with six openings, composed of pure
silex, and in many species is exquisitely ornamented. Figs. 8 and 9.
show a living _Navicula_, viewed in front, and in profile: in _fig. 9_
are represented the currents produced when the body is moving through
the water; after Ehrenberg. Fossil _Naviculæ_ abound in many tertiary
strata.
_Galionella._ _Plate IV. figs. 10, 11._--These algæ are free, and the
frustules of a cylindrical, globular, or discoidal form; they occur in
chains, in consequence of the self-division being imperfect, and the
new individuals remaining attached to the old. The _Galionellæ_ are
most abundant and prolific, and inhabit every pool, stream, and lake:
fossil species occur in the Virginian marls, and other strata.
_Synhedra._ _Plate IV. fig. 12._--The frustules are siliceous, and of a
slender, elongated form. The plant is attached by the base (_fig. 12
a._) in youth, and afterwards becomes free. It is found fossil in the
Mountain-meal of Santa Flora, and many other deposits.
_Podosphenia._ _Plate IV. fig. 13._--The frustule is cruciform, or
wedge-shaped, and attached in youth by the small end, but afterwards
becomes free. These plants are often arranged in clusters, as in
the figure. M. Ehrenberg states that they inhabit the sea, and not
fresh-water; but I have found them in streams communicating with the
Thames. _Podospheniæ_ abound in the polishing slate of Bilin.
_Eunotia._ _Plate IV. figs. 16, 17._--The frustule is siliceous, and
either simple or bivalve; flat below, and convex, and often richly
dentated above. An empty case is shown _fig. 16_; and a group of living
_Eunotice_ attached to a stem of conferva, _fig. 17_. Several fossil
species have been discovered at Santa Flora.
That the general reader, whose attention is for the first time
directed to this subject, may be prepared for the enormous deposits
of fossil diatomaceæ that are found in some formations, I subjoin the
observations of Dr. Bailey on an elegant fragile species, which hangs
together in clusters, appearing like spiral chains, and is about 1/20
of a line in diameter; it is named _Meridion vernale_.
"This fresh-water plant is seen in immense quantities in the mountain
brooks around West Point, the bottoms of which are literally covered
in the first warm days of spring with a ferruginous-coloured mucous
matter, about a quarter of an inch thick, that, on examination by the
microscope, proves to be filled with millions and millions of these
exquisitely beautiful siliceous organisms. Every submerged stone, twig,
and spear of grass, is enveloped by them; and the waving plume-like
appearance of a filamentous body covered in this manner, is often
extremely elegant. Alcohol completely dissolves the endochrome (_soft
colouring matter_) of this species, and the frustules are left as
colourless as glass, and resist the action of fire."[64]
[64] Trans. Amer. Assoc. Geolog. 1843, p. 152.
The yellow or ochreous scum observable in ponds, ditches, and
stagnant pools, is an aggregation of diatomaceæ, whose frustules are
feriniginous, and of such extreme minuteness, that a billion of their
cases would not be more than a cubic inch in bulk.[65]
[65] Ehrenberg.
Fossil Diatomaceæ.--From this notice of a few recent types, we proceed
to the investigation of the fossil remains of this tribe of Algæ.
In peat-bogs and swamps, both of modern and ancient date, masses of
a white marly or siliceous paste (_hydrate of silica_), are often
observed, and these are found upon microscopical observation to
be wholly made up of the frustules of _Naviculæ_, _Bacillariæ_,
_Galionellæ_, &c., with an intermixture of the needle-like spicules of
fresh-water sponges. Many of the peat-bogs of Ireland contain layers of
a white earthy substance, which, when dry, is of the appearance and
consistence of friable chalk, and entirely consists of the siliceous
cases of various kinds of diatomaceæ.
[Illustration: Lign. 4. Siliceous Frustules of Diatomaceæ, and Spicules
of Spongillæ; from a deposit on the banks of the river Bann, Ireland.
(_Seen by transmitted light, and highly magnified._)]
[Sidenote: FOSSIL DIATOMACEÆ OF IRELAND.]
Fossil Diatomaceæ from Ireland, _Lign. 4._--Dr. Drummond describes
a bed of this kind near the base of the Mourne Mountains, in the
County of Down, Ireland. It consists of a very light white substance,
resembling in appearance carbonate of magnesia: it has a coarse and
somewhat fibrous fracture, and is easily reduced to powder. It is
almost entirely siliceous, and is composed of the cases of diatomaceæ
of the usual fresh-water species, without any admixture of inorganic
matter.[66]
[66] Mag. Nat. Hist. New Series, vol. iii. p. 353, July 1839.
On the banks of the river Bann, in the same county, there is an
extensive stratum of a similar earth, and which, from being in much
request for polishing plate, is locally known as Lord Roden's plate
powder. This earth is wholly made up of the siliceous frustules of many
kinds of this tribe of Algæ, and a few grains under the microscope
yield a great variety of exquisite forms: figures of several are
given in _Lign. 4_, from specimens of this earth, with which I was
favoured by the Countess of Caledon. They comprise two or three species
of Navicula, Galionella, Coscinodiscus, Gomphonema, Bacillaria,
Stauroneis, &c., and spicules or spines of fresh-water sponges.[67]
[67] The names of the usual kinds of Diatomaceous frustules may be
learnt by reference to Mr. Andrew Pritchard's abstract (with coloured
figures) of Ehrenberg's Infusoria. The splendid work of Mr. Ralfs, on
the British Desmidieæ, 1 vol. 4to, with coloured plates, is the best
guide for those who wish to study the recent plants.
Beds of siliceous marl--that is, of argillaceous earth combined with
a large amount of minute particles of silex, all of which prove to be
organisms when examined by a high magnifying power,--have been found in
numerous places not only in England, but all over the world, since M.
Ehrenberg first directed attention to their nature and origin.
Near Bryansford (Newcastle), Binstwick in Holderness, and in the Fens
of Lincolnshire and Cambridgeshire, extensive fresh-water microphytal
deposits have been discovered and examined.
From our Antipodes I have received many examples of these vegetable
earths. My eldest son, Mr. Walter Mantell, discovered an extensive bed
of white marl on the banks of the great brackish-water lake of Waihora,
in the middle island of New Zealand, consisting entirely of frustules
of Bacillariæ. From New Plymouth he obtained some new and exquisite
forms of Navicula, Stauroneis, &c.; ranges of low hillocks of sand,
of considerable extent, being made up of microphytes (_microscopic
plants_).[68]
[68] See a Memoir on the Geology and Fossil Remains of New Zealand,
from the researches of Walter Mantell, Esq.--_Geol. Journal_, vol. vi.
_pl._ 29.
Mr. Dean, of Clapham Common, informs me that a large quantity of white
earth sent from New Zealand as native magnesia, he found to consist
wholly of frustules of diatomaceæ, chiefly of _Galionellæ_. (See _Lign.
5._)
[Illustration: Lign. 5.
Fossil. Galiomellæ; _highly magnified_.]
In America, recent beds of this kind of great extent have been observed
and examined by that distinguished microscopist, Dr. Bailey, Professor
of Chemistry in the Military Academy at West Point: and the pages of
that excellent scientific periodical, Silliman's _American Journal of
Science_, are enriched with figures and descriptions of the microphytes
of which they are mainly composed.
But the Tertiary formations contain strata of this nature, which far
surpass in the abundance and variety of their organic contents, any
of the modern deposits we have noticed. The _Polierschiefer_, or
_polishing-slate_ of Bilin, is stated, by M. Ehrenberg, to form a
series of strata fourteen feet in thickness, entirely made up of the
siliceous shells of _Galionellæ_, of such extreme minuteness, that
a cubic inch of the stone contains forty-one thousand millions. The
_Berghmehl_ (_mountain-meal_, or _fossil farina_), of San Flora, in
Tuscany, is one mass of these organisms.
In Lapland a similar earth is met with, which, in times of scarcity, is
mixed by the inhabitants with the ground bark of trees, for food; some
of this earth was found to contain twenty different species of algæ.
In the district of Soos, near Egra, in Bohemia, a fine white infusorial
earth occurs, about three feet beneath the surface; this substance,
when dried, appears to the naked eve like pure magnesia, but under the
microscope is seen to be mainly constituted of elegant disciform cases
of a species of _Campilodiscus_, of which figures are given, _Lign.
111, figs. 1, 2_.
Some beds of porcelain-earth M. Ehrenberg found to be in a great
measure made up of concentric articulated rings, entire and in
fragments (see _Lign. 6_), which he believes to be bacillariæ.
[Illustration: Lign. 6 Organic Bodies in Porcelain Earth; _highly
magnified_.]
[Sidenote: FOSSIL DIATOMACEÆ OF VIRGINIA.]
Fossil Diatomaceæ of the Richmond-earth; Virginia.--The town of
Richmond, in Virginia, is built on strata of siliceous marl of great
extent, which earth; highly magnified. have a total thickness, beneath
and around the town, of more than twenty feet. These marls, whose
organic composition was first detected by Professor W. B. Rogers, are
referred by that eminent American geologist, to the older tertiary
(_eocene_, or _miocene_) formations. They occupy considerable
districts, spreading out into sterile tracts along the flanks of
the hills, their siliceous character rendering them unfavourable to
vegetation. The investigations of Dr. Bailey have shown that the
frustules so abundant in this earth, consist of several species of
Navicula (_Lign. 1, fig. 1, 1a_.), Galionella (_Lign. 1. fig. 3,
3a_.), _Actinocyclus_ (_Lign. 1, figs. 4, 5_), &c.
The most remarkable forms are disciform frustules, having their
surfaces elaborately ornamented with hexagonal spots disposed in
curves, and bearing some resemblance to the engine-turned case of a
watch. _Lign. 7, fig. 2_, is a small segment of a disc, very highly
magnified. These frustules vary in size from 1/100 to 1/1000 of an inch
in diameter; they are named _Coscinodiscus_ (_sieve-like disc_), and
there are several species: one less richly sculptured, _C. patina_, is
figured _Lign. 7, fig. 6_. Circular bodies, with five or six lines
radiating from the centre to the circumference, like the spokes of
a wheel, hence named _Actinocyclus_ (_Lign. 7, figs. 4, 5_), and
spicules of Sponges, are also abundant.
[Illustration: Lign. 7. Microphytes[69] from the Richmond-earth;
_highly magnified_.
_Tertiary. Virginia._
Fig. 1.--Navicula. 1_a_. Side view.
2.--Coscinodiscus radiatus; a portion of the circular shield.
3.--Galionella sulcata; the upper figure shows the transverse
face of one of the frustules.
3_a_.--Three united cells viewed laterally.
4, 5.--Actinocyclus. Two species.
6.--Coscinodiscus patina; transverse view.
6_a_. Lateral view.
]
[69] As the term _Infusorial-earth_ must be abandoned, it will be
convenient to substitute a name simply expressive of the nature of
the most abundant organisms that enter into the composition of these
deposits: that of _Microphyta_, or _Microphytes_, (from μικρος,
_mikros_, small, and φυτον, _phyton_, a plant), signifying very
minute vegetables, may perhaps be admissible: in this sense the word
microphytal is employed in these pages.
When a few grains of the marl are prepared, and mounted on a glass,
almost all these varieties will be manifest, so largely is this earth
composed of organic structures; in fact, very few inorganic particles
are intermixed, the merest pellicle left by the evaporation of a drop
of water in which some of the marl has been mixed, teeming with the
most beautiful structures.
At Petersburg, in Virginia, a sandy marl occurs, interstratified with
deposits which, from their shells, are referred to the older tertiary
formations. Probably this marl is a continuation of that of Richmond,
but it is full of many new forms, associated with those common in the
earth of the latter locality.[70]
[70] Dr. Bailey, with great liberality, has so amply supplied myself
and other observers with specimens of these deposits for examination,
that the fossils above described are familiar to all British
microscopists. Figures of many of those organisms are given in the
American Journal of Science.
It is an interesting fact, (first observed by Mr. Hamlin Lee,) that the
common Scallop (_Pecten maximus_), as well as the Barnacle (_Balanus_),
feed on diatomaceæ, and their stomachs generally contain numerous cases
of Coscinodisci, Dichtyochi, Actinocycli, &c.: a slide prepared and
mounted with the contents of the stomachs of these mollusks, presents
an assemblage of forms identical with those found in the tertiary
earths of Virginia.[71]
[71] See my "Thoughts on Animalcules," p. 103.
In the mud of the quicksands on the shore at Brighton, Mr. Reginald
Mantell found recent Coscinodisci, &c. associated with fossil
polythalamia that had been washed out of the chalk, and precipitated
with the frustules of the recent diatomaceæ, into the sediments now in
progress.
The prevalence of marine and fresh-water forms in the same deposit
is not unusual; and the remarks of Dr. Bailey on this fact are so
pertinent, that I insert them, as a salutary caution against hasty
generalizations on subjects connected with these investigations.
After describing a species of Galionella (_G. moniliformis_), as an
inhabitant only of salt and brackish water, and stating that he had
also found it sixty miles up the Hudson River, near West Point, Dr.
Bailey observes--"The Fauna and Flora of the Hudson at this place
would, if in a fossil state, be rather puzzling to the geologist, on
account of the singular mixture of marine and fluviatile species. While
_Valisneria_ and _Potamogeton_ (two common fresh-water plants), grow
in such vast quantities, in some places, as to prevent the passage
of a boat, and the shore is strewn with fluviatile shells (such as
Planorbis, Physa, &c.) in a living state, yet the above plants are
entangled with Algæ (sea-weeds), and marine parasitic zoophytes; while
the rocks below low-water mark are covered with Balani (_barnacles_)
and minute corallines, and the marine Flora is represented by vast
quantities of very elegant sea plants."[72]
[72] American Journal of Science, vol. x. p. 41.
* * * * *
I must here close this extended notice of the fossil remains of a class
of vegetable organisms, which, though for the most part invisible
to the unassisted eye as individual forms, constitute by their
inconceivable multitudes an important element in the formation of
sedimentary deposits. The fact of their having been formerly treated
of as animalcules, and generally regarded as belonging to the animal
kingdom, rendered a full consideration of the phenomena necessary,
in order to place the subject before the reader in a clear and
comprehensive point of view.[73]
[73] As both the recent and fossil frustules of Diatomaceæ are
beautiful objects for the microscope and polariscope, they are in much
request. Specimens mounted on glass slides may be had of Mr. Topping,
and Mr. Poulton. See Appendix.
Confervites.--The cellular aquatic plants named Confervæ are sometimes
found in transparent quartz pebbles, and in chalk, appearing as
delicate simple or branched filaments, which, by the aid of the
microscope, are seen to be articulated. Seven species are described
by authors, but the vegetable nature of some of these is doubtful. A
beautiful species in Chalk, first noticed by the late Samuel Woodward,
Esq. (author of the Geology of Norfolk), is here figured.
[Illustration: Lign. 8. Confervites Woodwardii; _nat._
_Chalk. Norfolk._]
[Sidenote: FOSSIL FUCOIDS.]
Fossil Fucoids.--Of the tribe of Algæ which comprises the sea-weeds
that are not articulated, many fossil species occur in very ancient,
as well as in modern, fossiliferous deposits. In the Lower Silurian
rocks of North America, beds of limestone of great extent are full of
a large digitated Fucus (_Fucoides Alleghaniensis_).[74] The Firestone
or Malm-rock of Bignor in Sussex abounds in a ramose variety (_Fucoides
Targionii_, _Vég. Foss._ p. 56), of which specimens are figured in the
vignette of this volume, and in _Lign. 9._
[74] Figured and described in Dr. Harlan's Medical and Physical
Researches: Philadelphia, 1835, p. 393.
Chondrites.--These fossil algæ approach nearest to the living species
of _Chondrus_ (hence the name of the genus). The frond is thick,
branched, dichotomous, with cylindrical or claviform divisions, with
a smooth surface and without tubercles. The substance of the Bignor
fossils is a white friable earth, which strikingly contrasts with
the dark grey malm-rock that forms the matrix. As the Sussex Chalk
Chondrites appear to be distinct from the Tertiary species named by M.
Brongniart _C. Targionii_, I have, at the suggestion of Mr. Morris,
substituted _C. Bignoriensis_, to indicate the locality in Sussex in
which I discovered it forty years since. In the chalk-flints ramose
fuci occasionally occur, but not in a state of preservation that admits
of the determination of the forms of the originals.
[Illustration: Lign. 9.
Chondrites Bignoriensis; _nat._
_Malm-rock. Bignor, Sussex._]
The tertiary marls and limestones of Monte Bolca yield several
beautiful species of Algæ, one of which is figured in _Lign. 10_. It is
referred to the fossil genus _Delesserites_ (Sternberg), which includes
those algæ that have thin, and flat or undulated, smooth, membranous
fronds, with a median rib.
Of the little plants comprised in the class of cellular cryptogamia,
which have stems, leaves, and fructification, but no true vessels, two
or three species of Moss and Liverwort have been met with in tertiary
strata. Mosses as well as Fuci are occasionally imbedded in quartz
pebbles, in which they appear of their natural colour, and apparently
floating in the transparent medium. A beautiful green moss, with a
Conferva twined round its base, is figured _Lign. 11_ , p. 104, from a
specimen described by the late Dr. Macculloch. It is supposed to be
related to _Hypnum_ (_Geol. Trans._ vol. ii.).
[Sidenote: MOCHA-STONES.]
Moss-agates and Mocha-stones.--The beautiful siliceous pebbles called
Moss-agates, and Mocha-stones, will so often come under the notice
of the collector, that, although but extremely few, if any, of these
objects contain organic remains, the arborescent substances they
inclose being merely metallic oxides, a few remarks on their nature
may be expected. The late Dr. Macculloch paid considerable attention
to the investigation of these bodies, and believed that some of
the objects imbedded in the pure and compact quartz were really of
vegetable or animal origin; the specimen figured _Lign. 11_ is of this
kind; the fossils being apparently cellular cryptogamous plants. In
_Geol. Trans_, vol. ii., other examples are figured and described by
the same sagacious observer. Mr. Bowerbank is of opinion that spongeous
structure enters into the composition of almost all the moss-agates,
and I have no doubt that in some instances such organisms are present:
but in by far the greater number of agates and mocha-stones the
inclosed bodies are mere crystallizations; they are arborescent or
dendritical oxides of manganese, copper, chlorite, iron, &c.
[Illustration: Lign. 10 Delesserites (Fucoides) Lamourouxii.
_Monte Bolca._ (_Vég. Foss. Br._)]
[Illustration: Lign. 11.
Moss and Conferva, in transparent quartz, × 3.]
M. Brongniart, who carefully examined a great number of agates and
pebbles, with the view of determining if vegetable substances were
ever imbedded in them, could not detect a single instance in which
the apparent mosses, confervæ, or algæ, were organic; in every case
the mineral origin of the pseudo-vegetation was, in his opinion,
unequivocal. Some of the beautiful green arborescent bodies in quartz
pebbles, even under the microscope, present so close a resemblance to
confervæ and mosses, that it is difficult to persuade oneself they are
not vegetable structures; but the observations of M. Brongniart appear
to me conclusive as to their mineral nature.[75] With the exception of
three or four species of _Jungermannia_, and four or five of _Muscites_
in Amber, M. Brongniart states that he knows but one true fossil plant
of the family of Mosses; the _Muscites Tournalii_ from the fresh-water
tertiary deposits of Armissan.
[75] See Histoire des Végétaux Fossiles, pp. 29-34.
Vascular, or Acrogenous Cryptogamia.--These plants, as the name
implies, possess a more complicated structure than the preceding,
having vascular tissue as varied as in the phanerogamia.
Equisetaceæ.--The common species of Equisetum, or Marestail, is a plant
that grows in marshy tracts, and on the banks of ditches and rivers; it
has a jointed stalk, garnished with elegant sheaths which embrace the
stem, and verticillate linear leaves: it attains a height of two feet,
and is half an inch in diameter. In the fossil state there are many
plants allied to the Equisetum, but only a few that are generically the
same.
[Illustration: Lign. 12. Equisetum Lyellii.
_Wealden. Pounceford._ _nat._
Fig. 1.--A stem, having two sheaths, and a bud at the lowermost joint.
2.--Stem of a young plant, with sheaths, preserved in pyrites.
3.--Stem, with the cryptogamous head or upper end.
]
[Sidenote: EQUISETITES.]
Equisetum Lyellii, _Lign. 12_.--A species which I discovered in Wealden
limestone, at Pounceford (_Geol. S. E._ p. 245), must have closely
resembled the _Equisetum fluviatile_: it has an articulated cylindrical
stem, and regularly dentated sheaths, embracing the stem at the joints.
A transverse slice of the stem exhibits under the microscope a cellular
structure filled with calc-spar, and forms a beautiful object when
viewed with the polarizing apparatus. This plant occurs in many
localities of the Wealden in Sussex and Kent; from the railway cuttings
near Tonbridge, I collected several fine specimens; it is met with also
in the cliffs near Hastings.
Equisetites columnaris. _Lign. 13_.--A gigantic species of Equisetum
abounds in the strata of the lower division of the Oolitic or Jurassic
formation of Yorkshire, and many fine specimens have been collected,
especially from the vicinity of Whitby. In the sandstone of the
Inferior Oolite of the Cleveland Hills, Yorkshire, numerous stems
of this colossal marestail have been observed standing erect, as if
occupying the position in which they grew; the same fact was also
discovered at Carlton Bank, near Stokesly, forty miles from the coast.
In both localities fossil shells of fresh-water mussels (_Uniones_)
were associated with the vegetable remains.
[Illustration: Lign. 13. Equisetites columnaris.
(Ad. Brongn. Pl. 13.)
_Lower Oolite. Whitby._
Fig. 1.--Portion of a stem, showing two articulations, and an
intermediate constriction. 1/3 _nat._
2.--A few of the denticulations produced by the sheath, _nat._
]
This plant is a true equisetum, differing chiefly from existing species
in its gigantic size and arborescent character. The sheaths surrounding
the stem, and the verticillate linear leaves, are preserved in some
examples: and in all, the furrows left by the imprints of the sheaths
are more or less strongly impressed. The stem is not channelled
throughout, as in _Calamites_, the carboniferous plant whose stems at
first sight might be mistaken for those of Equisetites, but which are
entirely distinct, as will be explained hereafter. The Equisetites
columnaris is peculiar to the Oolite; it does not occur in the
coal-measures. Specimens have been discovered which indicate a height
of twenty feet, and a diameter of several inches.[76]
[76] See Hist. Vég. Fossiles, p. 115.
A small species of Equisetum (_Eq. Brodiei_[77]) occurs in
the insectiferous limestone of the lower Lias, at Strensham,
Worcestershire, associated with the foliage of fresh-water endogenous
plants resembling the _Potamogeton_, or pond-weed, and of supposed
dicotyledonous vegetables.
[77] Prof. Buckman, in Geol. Journal, vol. vi. p. 413.
[Illustration: Lign. 14. Calamites decoratus.
1/3 _nat._
(Ad. Brongniart. Pl. 14.)
_Coal Formation. Yorkshire._
Fig. 1.--Part of a stem, showing the tubercles for the attachment
of leaves.
2.--A portion of the same on a larger scale.
]
[Sidenote: CALAMITES.]
Calamites. _Lign. 14, 15_.--Stem articulated, regularly furrowed
longitudinally, the articulations naked, or studded with tubercles.
The plants of this genus were supposed to be related to the marestail,
but to differ in the absence of the encircling sheaths, and in being
uniformly striated; but an examination of specimens in a better state
of preservation than those previously known, shows their affinity to
the gymnosperms. Some of the species are of a gigantic size, being from
one to three feet in diameter, and from thirty to forty feet in height.
Calamites abound in the coal formation, and must have constituted an
important feature in the forests of the carboniferous period; they
occur also in more ancient deposits, and some species belong to the
earliest terrestrial Flora of which any vestiges are known. In most
instances when specimens are found lying in the same plane with the
strata, they are pressed flat, but those occurring in a vertical
position retain their natural cylindrical form. An outer crust or
cylinder of coal generally invests the stem, but traces of the internal
structure are rarely preserved.
The Calamite consists of a large central column of tissue, surrounded
by a ligneous cylinder. The central part has in most instances perished
after the death of the plant, and the cavity thus left been filled
up with mineral matter. As the hollow ligneous zone is almost always
carbonized, and very friable, it is seldom attached to the cast, and
consequently the surface of the latter is generally jointed and ribbed.
The true external surface of the cortical investment is marked with
longitudinal striæ, without any indications of joints or constrictions;
but the position of the original articulations is indicated in some
specimens by the _presence of small verticillate scars, to which leaves
were appended_[78] as in the example figured by M. Brongniart, of which
_Lign. 14, fig. 1_, is a reduced figure.
[78] See Mr. Dawes, "On the Structure of Calamites," Proc. Geol. Soc,
1851, vol. vii. p. 197.
[Illustration: Lign. 15. Calamites, in Coal Shale.
Fig. 1.--Calamites radiatus, with the remains of one of the
sheaths.--1/2 _nat._
2.--Stem, with remains of roots.--1/2 _nat._
3.--Calamites approximatus, showing the curved lower end of the
plant.[79]--1/5 _nat._
]
[79] This specimen has been inadvertently drawn with the base uppermost.
The stellate appearance on the upper part of the stem figured in
_Lign. 15, fig. 1_, is produced by the zone of leaves which
surrounded the joint: this character is entirely distinct from the
sheath of the Equisetum shown in _Lign. 12_. This specimen points out
the importance of carefully examining and preserving the stone around
fossil stems; had this precaution been lost sight of in this instance,
no knowledge would have been obtained of this important botanical
character. It is rarely that any traces of the roots remain; the fossil
figured (_fig. 2_) is from the _Foss. Flor._ A beautiful example of the
foliage of a species of Calamites is represented in _Lign. 59, fig.
2_.
Upright stems of Calamites occur in the Coal formation near Pictou,
in North America; and in one example a group of ten or twelve stems,
covering an area of two square feet, sprung from one root.[80]
[80] Dawson, Geol. Proc. vol. vii. p. 195. See Sir C. Lyell's Travels
in North America, vol. ii. p. 195.
* * * * *
[Sidenote: FOSSIL FERNS.]
Filicites, or Ferns.
We now arrive at the consideration of one of the most interesting
families of the vascular cryptogamia that adorned the Flora of the
ancient world, and the living species of which impart beauty and
elegance to the scenery of the countries where they prevail. The most
essential character of these vegetables, is that of developing their
fructification on the leaves; a fact familiar to every one who has
even but cursorily examined the Polypody growing on our walls, or the
Brake of our hedge-rows and commons. The largest species of British
ferns scarcely exceed four or five feet in height; but the arborescent
or tree-ferns, of warm climates, attain an altitude of from thirty to
forty feet. There is too this peculiarity in the arborescent forms,
that while in our indigenous species the leaves surround the stem, and
incline towards the upper part of the plant, the foliage of the former
bends downwards, and spreads out from the crown, or summit, into an
elegant canopy.
[Illustration: Lign. 16. Pecopteris Sillimani; _nat._
_Coal Shale. Ohio._
_a._ The Stem.
_b._ Leaf-stalk, or petiole.
_c._ Leaf, or frond, which is bipinnate.
_d._ _e._ Leaflets, or pinnæ; the upper, _d_, are entire;
the lower, _e_, are pinnatifid.
_f._ The pinnules, lobes, or segments.
_g._ The midrib, or median vein.
_h._ The veins. The veins are introduced in the leaflets,
_d_; but in the lower ones, _e_, the midribs
only are marked.
]
The leaves of our branched ferns are persistent, and when shed, the
markings left by their attachment to the stalk are soon obliterated. In
the arborescent ferns, on the contrary, the petioles become detached
from their bases, and fall entire, leaving scars or cicatrices on
the stem; and these impressions are so regularly and symmetrically
disposed, as to afford characters by which the trunks may be
distinguished from those of other trees. The stems of the tree-ferns
are therefore easily recognized in a fossil state externally, by their
cylindrical forms without ramification, and by the regular disposition
and peculiar character of the scars left by the separation of the
petioles; and, internally by that peculiar zone, formed of bundles
of ligneous tissue inclosed in sheaths, which encircles the central
axis, as shown in the transverse sections in _Lign. 2_, _ante_, p.
62. The leaves may be identified by the form of their segments, which
are disposed with remarkable regularity, and have a peculiar mode of
subdivision; and above all, by the delicacy, evenness, and distribution
of the veins. There are upwards of two thousand species of living
ferns, and in the fossil kingdom the number is considerable; more than
two hundred have been collected from the carboniferous formation. The
recent tree-ferns are confined almost exclusively to the equinoctial
regions; humidity and heat being the conditions most favourable to
their development (_Vég. Foss._ p. 141. _Bd._ p. 461. _Wond._ p. 727).
From the elegance and diversity of form of their foliage, fossil ferns
are the most remarkable and attractive vegetable remains in the ancient
strata. The greater number are from the coal deposits, the fern-leaves
generally occurring in the schists or shales that form the roof of the
beds of coal. Many of the strata are made up of carbonized fern-leaves
and stems closely pressed together. The roof of a coal-mine, when
newly exposed, often presents a most interesting appearance, from the
abundance and variety of leaves, branches, and stems, that occur either
in relief, or impressed on the dark glossy surface. The specimens
selected for illustration exhibit the principal modes of venation on
which the genera are founded.
* * * * *
The fossil genera have been established by M. Ad. Brongniart, from
the form of the leaves and the characters of their venation; that is,
the distribution of the vessels. In the following descriptions some
botanical phrases are necessarily employed; a few terms of frequent
occurrence are explained in _Lign. 16_.
Pachypteris[81] (_thick-fern_). _Lign. 17._--In this genus from the
lower Oolite, the fronds are pinnated, or bipinnated, the leaflets
entire, without visible veins, having but a single midrib, and
contracted at the base. The absence of veins, and the leaflets not
being lobed, are the essential generic distinctions.
[81] The names of the genera are derived from _pteris_, fern, to which
prefixed a term indicative of the peculiar characters.
[Illustration: Lign. 17. Pachypteris lanceolata.
_Inferior Oolite. Whitby._]
[Illustration: Lign. 18. Sphenopteris elegans
_Coal-shale, Waldenburg, Silesia._]
[Sidenote: FOSSIL FERNS. SPHENOPTERIS.]
Sphenopteris (_wedge-leaf_). _Lign. 18_.--The leaves are twice or
thrice pinnated, the leaflets wedge-shaped, contracted or narrowest
at their base, and more or less deeply lobed: the lobes divergent and
palmated: the veins radiating from the base.
The ferns of this genus are extremely elegant, and comprise upwards of
forty species. A beautiful Sphenopteris (_S. affinis_, _Wond._ p. 716,)
occurs abundantly in the fresh-water carboniferous strata at Burdie
House, near Edinburgh;[82] another elegant form, in coal-shale, is
represented in _Lign. 18_.
[82] See Dr. Hibbert's Memoir on the Strata and Fossils of Burdie
House. 4to. 1835.
[Illustration: Lign. 19. Sphenopteris nephrocarpa.
_Inferior Oolite, Scarborough._
A magnified vein of a leaflet, showing the fructification at the
extremities of the lobes, × two diameters.]
It is so rarely that the fructification of any species of Sphenopteris
is preserved in a fossil state that I am induced to figure a leaflet
of a remarkable plant, of this genus from the fluvio-marine oolitic
deposits of Scarborough. _Lign. 19_ is copied from the lithograph
accompanying a notice of some rare plants from that locality, by the
eminent botanist, C. J. F. Bunbury, Esq.[83]
[83] Geol. Journal, vol. vii. p. 179, pl. xii.
This fossil fern closely resembles certain species of _Dicksonia_
(natives of New Granada). Each segment of the leaflet or pinnate
is dilated at the apex into a reniform _indusium_; no capsules are
visible, the fructification being, probably, in a young state.
[Illustration: Lign. 20. Sphenopteris Mantelli; _nat._ _Wealden,
Tilgate Forest._]
In the Wealden deposits, both of England and Germany, several species
of Sphenopteris abound; one of which (_Foss. Tilg. For._ 1827), often
occurs in the calciferous grit of Tilgate Forest, in a beautiful state
of preservation: a small branch is figured in _Lign. 20_. This species
is characterized by its slender and minutely divided wedge-shaped
leaflets. The Sphenopteris Mantelli did not attain a considerable size;
the largest stem I have seen indicated a plant of five or six feet in
height. This Sphenopteris is sometimes associated with the remains of a
beautiful plant of the genus _Alethoptris_,[84] the leaflets of which,
in some examples, bear the fructification. (_Wond._ p. 394, _Lign._ 89.)
[84] _Alethoptris elegans_ of Dr. Dunker. Mon. Norddeutschen Weald, pl.
vii. _fig. 7_.
[Illustration: Lign. 21. Cyclopteris trichomanoides; _a single
leaflet_; _nat._
_Oolite, near Scarborough._]
Cyclopteris (_round-leaf_). _Lign. 21._--The frond is simple and
entire, or but slightly lobed at the margin, and generally orbicular,
or kidney-shaped: there is no midrib; the veins are numerous, equal,
and dichotomous, or forked, and radiate from the base. The form and
disposition of the veins resemble those of some living species of fern;
the absence of a median rib, or vein, is the most striking character
of this genus. The fructification is supposed to have been marginal.
[Sidenote: FOSSIL FERNS. NEUROPTERIS.]
Neuropteris (_nerved-leaf_). _Lign. 22._--The fronds are pinnate or
bipinnate; the leaflets more or less ovate or cordiform and entire,
adhering to the rachis by their centre only; veins very fine, arched,
rising obliquely from the base of the leaflet; the midrib does not
extend' to the apex of the leaflets, but terminates by subdividing into
veins.
[Illustration: Lign. 22. Neuropteris acuminata; _nat._
_In Coal-shale, Yorkshire._]
This is a very numerous genus, comprising thirty or more species, which
are principally found in the coal-shale. Some of these plants bear
a general resemblance to the _Osmunda regalis_, but differ in their
essential characters; their leaflets often form the nuclei of ironstone
nodules.
Glossopteris (_tongue-leaf_). _Lign. 23._--Leaves simple,
sub-lanceolate, gradually contracting towards the base; midrib thick at
the base, and vanishing towards the apex of the leaf; veins very fine,
curved, oblique, frequently dichotomous, sometimes reticulated, or
anastomosing at their base. The plants of this genus resemble the ferns
with simple leaves. A few species only are known; of these, two are
from the coal-shale, one from the Lias, and one from the oolite.
[Illustration: Lign. 23. Glossopteris Phillipsii; _nat._
_Oolite, Scarborough._]
[Illustration: Lign. 24. Odontopteris Schlotheimii; _nat._
_Coal-shale of Saxony._]
Odontopteris (_tooth-leaf_). _Lign. 24._--Leaf bipinnate, the leaflets
adhering to the rachis or stalk by their whole base, which is not
contracted; the veins equal, simple, dichotomous, arising side by side
from the base of the leaflet; no distinct midrib. In their general
aspect these plants resemble some South American species of Osmunda.
Five species only are known, all of which belong to the most ancient
coal strata.
Anomopteris (_anomalous fern_--so named because the plants differ from
all recent and fossil ferns). _Lign. 25._--Leaves deeply pinnated;
leaflets very long, entire, linear, traversed by a distinct midrib,
equal throughout; secondary veins simple, perpendicular to the median
vein, swollen at their free extremities, and not extending to the
margin of the leaflet. But one species is known. These leaves are of
great size, and doubtless belonged to some arborescent fern; in several
examples the fructification is preserved. My collection contained a
splendid specimen from near Strasburgh, presented by the late M. Voltz,
which is now in the British Museum.[85]
[85] Petrifactions, p. 32.
[Illustration: Lign. 25. Anomopteris Mougeotii; _nat._
_New Red Sandstone; Sultz-les-Bains, near Strasburgh._
Fig. 1.--Three leaflets of a very large frond.
2.--A portion magnified to show the fructification.
]
[Sidenote: FOSSIL FERNS. TŒNIOPTERIS.]
Tœniopteris (_wreathed fern_). _Lign. 26._--Leaves simple,
entire, straight, with parallel margins, traversed by a strong
midrib, which extends to the apex; secondary veins, simple
or bifurcated at their base, and almost perpendicular to the
median vein. These ferns are related to certain species
of Polypodium. Three species are known; two from the
Oolite, and one from a tertiary deposit. The specimen
figured is a fragment.
[Illustration: Lign. 26. Tœniopteris latifolia; _fragment of a
frond; nat._
_Stonesfield Slate._]
[Illustration: Lign. 27.
Fig. 1.--Pecopteris Murrayana; a pinnule with the fructification;
_magnified._ _Inf. Oolite, Scarborough._
2.--Pecopteris lonchitica. _Coal-shale, France._
]
Pecopteris (_embroidered fern_). _Lign. 27._--Leaves once, twice, or
thrice pinnated: leaflets adhering by their whole base to the rachis,
rarely by the centre only; traversed by a strong midrib, which extends
to the apex; veins simple, or once or twice dichotomous, proceeding
almost at right angles from the median vein.
This genus embraces a very large proportion of the ferns which have
contributed to the formation of the coal, and whose leaves and
stems are preserved in the associated strata. The originals of many
species were undoubtedly arborescent, and attained a large size;
some leaves four feet wide, and of a proportionate length, have been
observed. More than one hundred species are determined. An American
species (_Pecopteris Sillimani_) is figured in illustration of
certain botanical terms, _Lign. 16_, _ante_, p. 110. Several species
of Pecopteris occur in the fluvio-marine oolitic deposits near
Scarborough, and leaves in fructification are not uncommon: _fig. 1,
Lign. 27_, represents a leaflet slightly magnified.
[Illustration: Lign. 28. Lonchopteris Mantelli.
_Wealden, Tilgate Forest._
Fig. 1 and 2.--Leaflets magnified, to show the reticulated venation.
3.--A fragment of a frond; _nat._
]
[Sidenote: FOSSIL FERNS. LONCHOPTERIS.]
Lonchopteris (_spear-leafed._) _Lign. 28._--Leaves many times pinnated;
leaflets more or less adherent to each other at their base, traversed
by a midrib; secondary veins reticulated.
The three known species which compose this genus resemble the living
ferns of the genera Lonchitis, Woodwardia, &c. Two have been found in
the coal-measures, and one species in the Wealden formation of England
and Germany (_Foss. Tilg. For._ pl. iii.) This last appears to have
been a delicate plant; for though fragments are very common in the
micaceous grits and clays, any considerable portion of a leaf is of
rare occurrence. M. Graves found the same fern near Beauvais in France,
in strata, which, from the presence of the fresh-water limestone called
Sussex marble, are supposed to be referable to the Wealden epoch. This
Lonchopteris is widely spread through the Wealden; and occurs also in
the Greensand. Mr. Morris first observed it in the iron-sandstone of
Shanklin Chine.[86]
[86] Geol. I. of W. 2d _Ed._ p. 230.
[Illustration: Lign. 29.
Fig. 1.--Phlebopteris[87] Phillipsii. _Oolite, Scorborough._
2.--Phlebopteris propinqua, _showing fructification_.
]
[87] Comptopteris of M. Ad. Brongniart.
Phlebopteris (_veined-leaf_). _Lign. 29._--Leaves pinnated; leaflets
with the margin entire, or crenulated, the midrib strong; secondary
veins anastomosing by arches, with large angular spaces, often
unequally disposed; the finer veins are simple or divided; the apex
sometimes free. The fructification is punctiform, and placed at the
apices of the veins.
The foliage of these remarkable ferns has been mistaken for the leaves
of dicotyledonous plants; but M. Brongniart has demonstrated that they
belong to the present family. Six species have been found in the Oolite
and Lias.
[Illustration: Lign. 30. Clathropteris meniscoides.
_Portion of a leaflet: the original 1-1/2 ft. long._
_Wealden? Scania._]
[Sidenote: FOSSIL FERNS. CLATHROPTERIS.]
Clathropteris (_latticed-leaf_). _Lign. 30._--Leaf deeply pinnatifid;
leaflets elongated, traversed by a strong midrib extending to the apex;
secondary veins numerous, simple, parallel, almost perpendicular to the
midrib, united by transverse branches, which, with the finer veins,
produce on the surface of the leaf a net-work of quadrangular meshes.
This genus was instituted by M. Brongniart, for the reception of
some very large fern-leaves from the shale of Hoer, in Scania,
which resemble in structure the foliage of the recent _Polypodium
quercifolium_, a native of the East Indies, and the Moluccas. One leaf
was four feet wide, and the leaflets, though imperfect, were eighteen
inches long.[88]
[88] Hoer is a little village, situated nearly in the centre of
Scania, a province in the southern extremity of Sweden. The Chalk
formation appears in several parts of this district, and Carboniferous
strata at Hoeganes. To the west of Hoer, there is a range of hills,
composed of ferruginous grits, micaceous sandstones, clays, and beds
of quartzose conglomerate. It is in these strata that the ferns and
other terrestrial plants occur, and no animal remains whatever have
been found in them; their geological position appears to be between
the Chalk and the Coal, but on this point nothing positive is known.
The general analogy of the plants with the group forming the Flora
of the Wealden, led M. Brongniart to suppose that the deposits in
question belong to that formation; and M. Nillson, of Lund, who
examined my collection at Brighton, recognized, among some undescribed
plants from Tilgate Forest, forms that he had collected from Hoer. See
"_Observations sur les Végétaux Fossiles renfermés dans les Grès de
Hoer en Scanie: par M. Ad. Brongniart._" _Ann. Sc. Nat._ 1825.
Many other genera of fossil ferns have been established from the form
and venation of the leaves, and are described in _Brit. Foss. Flor._,
and other British and foreign works.
Stems of arborescent Ferns.--Notwithstanding the profusion with which
the foliage of many kinds of ferns is distributed throughout the coal
formation, the undoubted stems of plants of this family are rarely
met with; for the numerous tribe called Sigillariæ is now removed
altogether from this class. It may, however, admit of question whether
much of the foliage which, from the analogy of structure, has been
referred to ferns, may not have belonged to those trees; for as in the
animal kingdom, so in the vegetable, distinct types of living organisms
are often found blended in the lost races; and as the stems of recent
tree-ferns are even more durable than their leaves, it seems impossible
to account for their absence in strata, that inclose entire layers of
the foliage matted together. A few fossils, supposed to possess the
essential characters of recent fern-stems, have been discovered, and
arranged under the following genus.
[Sidenote: FOSSIL FERN-STEMS.]
Caulopteris (_fern-stem_). _Lign. 31._--Stems not channelled, marked
with discoidal, oblong, or ovate scars, arranged longitudinally;
vascular cicatrices numerous.
[Illustration: Lign. 31. Caulopteris macrodiscus. _Coal._]
The fragment of stem here figured, resembles the trunks of some recent
tree-ferns in its proportions, and in the number, disposition, and
size, of the scars of the leaf-stalks; but these markings differ in
their more lanceolate form, and pointed terminations, and in their
peculiarly striated surface, from those of any known existing species.
Psarolites (_Silicified Fern-Stems_).--In the New Red sandstone, near
Hillersdorf, in the neighbourhood of Chemnitz, in Saxony, silicified
stems, apparently of tree-ferns, occur in great numbers. They are
remarkably beautiful, and the organization of the original is so well
preserved by the silex, that slices, examined by the microscope,
display the peculiar structure almost as perfectly as if the plants
were recent: transverse sections exhibit the arched bundles of vascular
fibres which compose the ligneous cylinder, surrounded by the cellular
tissue. From the stellated markings produced by sections of the vessels
that compose the tissues, and which are visible to the naked eye,
these fossils have obtained the popular name of _Staaren-stein_, or
Star-stone. The external surface of the specimens I have examined has a
ligneous structure, and is of a dark reddish brown colour; internally
the stems are of a dull red, mottled with various tints of blue and
yellow, from the infiltrated chalcedony with which the vessels are
permeated.[89]
[89] See Pict. Atlas (pl. viii.) for coloured figures; and Org. Rem.
vol. L plate viii. _figs._ 1-7. The reader will be amused by the
perusal of the ingenious but unsuccessful attempt of the excellent
author, Mr. Parkinson, to elucidate their nature. I have still a
specimen which he presented to me more than thirty-five years since, as
one of the most curious and perplexing fossils that had ever come under
his notice.
An excellent work ("_Dendrolithen_") on these fossils, in which thirty
species are described, has been published at Dresden by M. Cotta; who
arranges them under the genus _Psaronius_ or _Psarolites_. The stem is
composed of two distinct parts; an outer zone, consisting of a great
number of nearly cylindrical bundles of vessels, supposed to have been
roots which proceeded from the stem near its base; and an inner part
or axis. In the outer portion, the fossil _air-roots_ have a vascular
tissue, but there is often a delicate cellular tissue interposed. In
the axis the vessels form zigzag or wavy bands, resembling those of
ferns.[90] These flexuous and vermiform bands are entirely composed
of barred or scalariform vessels, similar to those of ferns and
club-mosses. The Psarolites are therefore considered by M. Ad.
Brongniart to be the bases of the trunks of lycopodiaceous trees, while
M. Cotta and other botanists regard them as true arborescent ferns.[91]
[90] Pict. Atlas, pl. viii.
[91] See M. Brongniart's "_Tableau des Genres de Végét. Foss._" p. 44.
Dr. Buckland has discovered in the New Bed sandstone formation at
Allesley, near Coventry, silicified trunks of coniferous trees, and it
is not improbable that further research in that locality may bring to
light fern-stems like those of Chemnitz.[92] Dr. Lloyd, of Warwick, has
recently obtained leaves of several coniferæ from the same locality.[93]
[92] Vide Geol. Proc. vol. ii. p. 438.
[93] Geol. Society, June 1852. Dr. Lloyd's specimens are probably
referable to the genus _Walchia_: see _Lign. 60._
[Sidenote: SIGILLARLÆ AND STIGMARIÆ.]
Sigillarlæ and Stigmariæ.
Among the most common and striking objects that arrest the attention
of a person who visits a coal-mine for the first time, and examines
the numerous vegetable relics that are profusely dispersed among the
heaps of slate, coal, and shale, are long flat slabs, from half an
inch to an inch thick, having both surfaces longitudinally fluted, and
uniformly pitted with deep symmetrical imprints; these are disposed
with such perfect regularity between the grooves, that the specimens
are often supposed, by persons not conversant with palæontology, to be
engraven stones, and not natural productions. These fossils are the
flattened trunks of gigantic trees covered by the bark in the state of
coal; the regular imprints on the surface, being the scars left by the
separation of the petioles or leaf-stalks, as in the arborescent ferns
previously examined. The name _Sigillaria_, commonly applied to these
fossils, is derived from _sigillum_, a seal, and alludes to the regular
and uniform pattern of the imprints on the surface. These stems are
from a few inches to several feet in diameter, and the largest attain
a height of sixty feet; they are generally found lying in a horizontal
position in the strata, and quite flat, from the pressure produced by
the superincumbent rocks; but when the trunks are in an erect position,
and at right angles to the plane of the beds, the cylindrical form of
the original is preserved.
A remarkable instance, in which five stems of Sigillaria were standing
upright, with their roots in the soil below, apparently in the position
in which they grew, was brought to light a few years since, in forming
the Bolton and Manchester railway.[94] They stand on the same plane,
and near to each other. Their roots are branched, and spread out in
the bed of impure coal in which they are implanted. The trunks are
surrounded by a soft blue shale. The largest tree is eleven feet high,
and seven and a half feet in circumference at the base; its trunk
is gnarled and knotted, and has many decorticated prominences, like
those in barked timber of our old dicotyledonous trees; the roots,
too, partake of the same character.[95] The others are respectively
from three to five feet in height. A sketch of one of the short stems
is subjoined. All the trees were broken off as if by violence, and no
traces of the upper part of the stems or branches were detected.
[94] These trees still remain _in situ_, and, thanks to the scientific
zeal of Mr. Hawkshaw, have been carefully preserved. They are situated
at Dixon Fold, Clifton, near Manchester. Instructive models of these
highly interesting relics of the carboniferous forests may be obtained.
An excellent Memoir on this discovery, with illustrations, by Mr.
Hawkshaw, is given in Geol. Trans, vol. vi. pl. xvii. See Pict. Atlas,
p. 198; and Petrifactions, p. 36.
[95] See Mr. Bowman's Memoir, Geol. Proc. vol. iii. p. 270.
[Illustration: Lign. 32. Base of a Trunk of a Sigillaria. with roots,
_standing erect with five other stems, in Carboniferous strata_.
(_The original is four feet high._)]
In the stratum through which the roots extend, a considerable quantity
of the fossil cones, called _Lepidostrobi_, hereafter described, were
imbedded (see _Lign. 40_). A thin layer of coal which invested the
stems, was evidently the carbonized bark. All the stems were filled
with blue clay, or shale, a proof that they were hollow when submerged
in the mud, which is now consolidated into the shale in which they are
imbedded. But it is not probable that they were originally tubular,
like a reed: on the contrary, there is evidence to show that they
were highly organized. Their internal structure may have decayed, or
been destroyed by insects or other depredators; as is often the case
in tropical climates, where the trunks of timber trees are speedily
excavated after their fall, and afford shelter to innumerable insects
and reptiles, as the weary traveller often finds to his surprise and
annoyance.[96] The late Mr. Bowman affirmed[97] that these trees were
dicotyledonous, and stated that medullary rays and coniferous structure
could be detected; an opinion, which the researches of M. Brongniart on
the Sigillariæ have fully corroborated.
[96] Mr. Hawkshaw, Geol. Proc. p. 269.
[97] Geol. Proc. vol. iii. p. 270.
* * * * *
[Sidenote: ERECT STIGMARIÆ.]
Many other instances have been noticed of Sigillariæ standing more or
less erect in the strata. In forming the railway tunnel at Claycross,
five miles south of Chesterfield, through the middle portion of the
Derbyshire coal-measures, in 1838, a group of nearly forty trees
(_Sigillariæ_) was discovered, standing not more than three or four
feet apart, at right angles to the plane of the strata.[98] On the
coast of Northumberland, within the length of half a mile, twenty trees
were observed by Mr. Trevelyan, in 1816 (_Bd._ p. 470). The coal-pit at
St. Etienne, in France, described by M. Alex. Brongniart, is celebrated
for affording an example of this phenomenon (_Wond._ p. 673); but the
positions of many of those stems are inclined at various angles, and
their roots implanted in different beds, so that the perpendicularity
of the erect trees is probably accidental (_Bd._ p. 471).
[98] Ibid. p. 272.
The most remarkable instance hitherto observed, is on the southern
shore of the Bay of Fundy, in Nova Scotia, where the cliffs, which are
about two hundred feet high, are composed of carboniferous strata,
consisting of coal, clay, grit, and shale, in which numerous erect
trees, probably Sigillariæ, are seen on the face of the cliff; there
are ten rows one above another, indicating, in the opinion of Sir C.
Lyell, repeated subsidences of the land, so as to allow of the growth
often successive forests![99] (_Wond._ p. 674).
[99] "On the Coal Strata of Nova Scotia." Amer. Journ. Oct. 1841 and
Travels in America, vol. ii. p. 180.
[Illustration: Lign. 33. Sigillariæ; _in Coal-shale_.
Fig. 1.--A specimen deprived of its carbonaceous bark, except in the
interstices of the channels, and showing pits left by the
external scars.
2.--The markings of S. Defrancii. (_Vég. Foss. Br._)
]
[Sidenote: SIGILLARLÆ.]
The stems of Sigillariæ vary in size from a few inches to five feet in
diameter; and in length from five to sixty feet; they gradually taper
from the base to the summit. A specimen measured by M. Brongniart was
forty feet long, one foot in diameter at the base, and but six inches
at the top, where it divided into two equal branches. These stems may
be readily distinguished from those of other trees with which they are
associated, by the fluted surface produced by the deep longitudinal
grooves, and the regularly disposed imprints between the channels.[100]
The carbonized bark, in large specimens, is often an inch thick, but
in small examples is a mere pellicle, and being extremely brittle,
flakes off with the slightest touch, leaving the inner surface exposed,
with the coal remaining in the deep furrows and pits, as in _Lign.
33, fig. 1_. No traces of leaves, or fruit, in connexion with the
stems, have been observed. The subjoined sketches (_Lign._ 33, and 34,)
illustrate the usual aspect of these fossils. The difference between
the imprints on the outside of the bark, and those on the exposed
surface of the stem, from the removal of the cortical covering, is well
marked in _Lign. 34_.
[100] The stems of some recent dicotyledonous trees from New Zealand, in
the possession of Dr. Robert Brown, possess similar longitudinal ribs
and furrows, both on the bark and alburnum, or naked wood.
[Illustration: Lign. 34. Sigillaria Saullii.
_Carb. Manchester._
_a._ The imprints of the petioles on the external surface of the
carbonized cortical investment.
_b._ The inner surface, exposed by the removal of the crust or bark.
]
Internal Structure of Sigillariæ.--Our knowledge of the structure of
this numerous tribe of plants, has received an important accession by
the discovery of the silicified fragment of a stem, which, fortunately
for the advancement of science, was placed at the disposal of M.
Adolphe Brongniart. It has been described and illustrated by that
eminent botanist, in a memoir which is one of the most valuable
contributions to fossil botany that has hitherto appeared.[101]
[101] The reader intending to make fossil botany his particular study,
should refer to the original memoir, and become familiar with the
facts and inferences so admirably enunciated by the author; not only
for the illustration of the structure of the tribe of plants under
consideration, but as a valuable exemplification of the manner in
which all such inquiries should be conducted. See _Archives du Muséum
d'Histoire Naturelle_, tom. i. Paris, 1839.
[Illustration: Lign. 35. Silicified Stem of Sigillaria elegans.
_Autun. France._ (_M. Adolphe Brongniart._)
Fig. 1.--A transverse section of the silicified stem, from Autun; _nat._
_a._ Situation of the medullary tissue, occupied by coloured
silex.
_b._ Zone composed of bundles of vessels, forming the woody
tissue.
_c._ Band of cellular tissue
_d._ Space between the ligneous cylinder and the bark, with no
evident structure, but originally occupied by the
external cellular tissue.
_e._ Zone of indistinct cellular substance.
_f._ External cortical envelopment, or bark.
2.--Portion of one of the vessels of the medullary tissue, as seen
in a longitudinal section, (× ×.)
3.--Portion of a spiral vessel of the same tissue. (× ×.)
]
The annexed figure (_Lign. 35_) is an outline of the specimen, of the
natural size; but this sketch is a mere plan or diagram, for it is
impossible without the aid of colour to convey a faithful idea of the
original. The student should observe, that when mineral matter has
permeated the stems of plants, the vascular tissue is often so well
preserved, that one such specimen affords more important information,
than hundreds of examples in which the form alone remains.
[Sidenote: SIGILLARLA ELEGANS.]
The external surface of this specimen possesses the characteristic
markings of the insertion of the leaf-stalks of _Sigillaria elegans_.
The internal organization, as seen in the transverse section, is as
follows:--
_a._ The centre, filled with silex; it exhibits no traces of structure.
_b._ The zone which surrounds the interspace on which this letter is
placed, is composed of bundles of vascular tissue. A portion of one of
these bundles, highly magnified, is represented in _Plate V. fig. 7_.
The _inner_ circle of this zone, indicated by the _convex undulating
line_, is made up of medullary vascular tissue; the external circle
is divided by rays, and is composed of woody fibre, constituting a
ligneous cylinder. One of the spiral vessels (_fig. 3_), and another
showing a remarkable difference of structure in a short space (_fig._
2), as seen in a longitudinal section of the medullary tissue, are
figured in _Lign. 35_.
The ligneous cylinder is surrounded by a band of cellular tissue, and
the space between this and the cortical integument is occupied by
silex, in which there are but obscure traces of structure.
The inner layer of bark, _f_, is composed of elongated cells, disposed
in a radiating manner, and traversed by fibro-vascular bundles, which
pass towards the leaves.
Upon instituting a comparison between the fossil and the stems of those
recent plants which present the closest analogy to it, M. Brongniart
was led to conclude that the Sigillariæ constituted a peculiar extinct
family, belonging to the great division of gymnospermous dicotyledons.
The Sigillariæ were tall erect trees, with a regular and cylindrical
stem, without side branches, but dichotomous towards the summit. Their
superficial bark was hard and durable, channelled longitudinally,
bearing leaf-scars that are of a rounded form above and below, and
angular at the sides, often oblong in relation to the stem, and having
three vascular pits, one central and small, and two lateral of a
larger size. The internal structure bears most analogy to that of the
Cycadeæ, and the foliage consisted of long linear carinated leaves.
The Sigillariæ, therefore, differ essentially from the arborescent
cryptogamia, which they somewhat approach in having scalariform
vascular tissue, symmetrical and regular leaf-scars, and branchless
trunks. More than fifty species have been determined.[102]
[102] For figures of Sigillariæ, see Pictorial Atlas, pl. xix. xx, xxiv.
[Sidenote: STIGMARIA.]
Stigmaria. _Lign. 36._--This extended notice of the structure of the
Sigillariæ,.will enable us to understand the nature of the fossil
vegetables termed Stigmariæ, or spotted-stems, which abound in the
beds of under-clay of most coal-fields, as stated in a former part
of this work (_ante_, p. 81). These bodies when uncompressed are of
a cylindrical form, from one to six or seven inches in diameter,
and of considerable length--sometimes upwards of twenty feet--and
gradually diminish in size towards their termination. The surface is
marked with distinct pits or areolæ, of a circular or oval form, with
a small tubercle in the centre of each, disposed around the stem in
a quincunx and somewhat regular order. When broken transversely, a
small cylindrical axis is seen to extend in a longitudinal direction
through the stem, like a medullary column; it seldom occupies the
centre, but lies near to one side, and parallel with a depression on
the outer surface of the fossil. This internal body is often loose,
and removable; its surface is covered with interrupted, irregular,
longitudinal, ridges, which leave corresponding depressions on the
walls of the cavity in which it was inclosed. _Lign. 36_, represents a
fragment exhibiting the characters above described.
[Illustration: Lign. 36. Stigmaria ficoides.
_Carboniferous. Derbyshire._--1/4 _nat._
Fig. 1.--Portion of a stem, with some of the rootlets (formerly
considered as leaves) extending into the surrounding
clay. The internal axis is seen at _a_; and the
corresponding groove on the portion of external surface
that remains.
2.--An outline of one of the rootlets, with a tubercle to show the
mode of its attachment by a ball and socket joint to the root.
]
When Stigmariæ are observed in the under-clay, to which stratum they
are principally confined, long, tapering, subcylindrical fibres, often
several feet in length, are seen affixed to the tubercles with which
the surface is covered; their form and mode of attachment are shown
in _Lign. 36_. Instances occur in which several Stigmariæ spring from
a common centre, of a dome-like form, whence they radiate in every
direction (_Bd._ pl. lvi. _fig._ 8), and the main branches divide and
subdivide till they are lost in the surrounding rock.
The nature of these fossil vegetables was long a perplexing question,
for no specimens had been found in connexion with any of the stems,
branches, or foliage, that abound in the coal deposits. At length,
the discovery of a dome-shaped mass, to which were attached numerous
Stigmariæ, seemed to afford a clue to the solution of this botanical
problem; and it was concluded by the eminent authors of the "Fossil
Flora of Great Britain," that the original belonged to a tribe of
plants which inhabited swamps, or still and shallow lakes, and were
characterized by a low truncated stem, having long horizontal branches
beset with cylindrical, and, probably, succulent leaves, that either
trailed on the surface of the swamp, or floated in the water.
But within the last few years, the occurrence in various carboniferous
deposits of erect stems of Sigillariæ, has shown that the Stigmariæ
are nothing more than the roots of these and other congenerous trees;
an opinion maintained by the Rev. H. Steinhaur more than thirty years
ago, and subsequently affirmed by M. Adolphe Brongniart, who found,
on examining microscopically the internal structure of a silicified
specimen in which the vascular tissue was preserved, that it bore as
close an analogy to that of the Sigillariæ, as exists between the roots
and trunks of certain dicotyledonous trees.
The annexed figure, _Lign. 37_, represents the transverse section of a
small Stigmaria, with the axis displaced from its natural situation;
this circumstance, as well as the corresponding external groove, has
arisen from compression, by which the tough cylinder has been forced
from its original position in the middle of the soft cellular tissue,
to one side.
[Illustration: Lign. 37. Transverse Section of Stigmaria ficoides;
_nat._
(_M. Adolphe Brongniart._)
This specimen shows that the cylinder (_a_ in _Lign. 36_) is formed of
bundles of vascular tissue, disposed in rays.]
The central axis is thus shown to be a cylinder composed of bundles of
vessels, disposed in a radiating manner, and separated from each other
by medullary rays; the whole constituting a ligneous zone resembling
that of Sigillaria (see _Lign. 35_); but the inner circle of medullary
tissue seen in the latter is altogether wanting. This difference is
similar to that observable in the stems or branches of a dicotyledonous
tree, in which the woody cylinder is associated internally with
bundles of medullary tissue, and the roots of the same tree that are
destitute of them. Part of a vascular bundle from the woody tissue of a
Stigmaria, seen by a high power and transmitted light, is figured _Pl.
V. fig. 6_; the smooth interspaces are composed of cellular tissue.
[Illustration: Lign. 38. Erect Stem of a Sigillaria, with roots.
_Coal Mine, near Liverpool._
_a._ The trunk of the tree, traversing a bed of Coal.
_b._ The roots (_Stigmariæ_) spreading out in the Under-clay.
]
[Sidenote: ERECT SIGILLARLA WITH ROOTS.]
This opinion of M. Brongniart was confirmed by the discovery, in 1843,
at St. Helen's, near Liverpool, of an upright trunk of a Sigillaria,
nine feet high, with ten roots eight or nine feet in length, still
attached, and extending in their natural position. _These roots
are undoubted Stigmariæ of the usual species, S. ficoides; and the
radicles, formerly considered leaves, are spread out in all directions,
to the extent of several feet._[103] To the sagacity and perseverance
of Mr. Binney, of Manchester, science is indebted for this important
discovery; the same gentleman laid bare, on the floor of the mine at
Dunkinfold, near Manchester, a large erect trunk of a Sigillaria, with
numerous Stigmariæ roots.
[103] From a communication to the British Association at Cork, 1843.
In the Pictou coal-field of Cape Breton, in Nova Scotia, similar facts
have been brought to light; the remarkable phenomena existing in that
locality, of successive carboniferous deposits containing scores of
erect trees with roots spreading into their native soil, presenting
peculiar facilities for verifying the observations made in England. In
an interesting memoir on the coal-fields of Nova Scotia, Mr. Richard
Brown has given a detailed account of numerous examples of stems of
Sigillariæ, and of Lepidodendra, (a tribe of gigantic club-mosses of
which we shall presently treat,) with the roots attached; these roots,
in every instance, had the characters and structure of Stigmariæ. In
one instance, the stem of the tree was broken off close to the roots,
and the hollow cylinder of bark was bent down and doubled over by the
pressure of the surrounding mud, so as effectually to close up the
aperture, and leave only a few irregular cicatrices converging near the
apex; this fossil explains the true nature of the "dome-shaped" plant
figured in the Fossil Flora, and in Dr. Buckland's Essay.[CZ]
[104] See Pictorial Atlas, p. 200: and Petrifactions, pp. 37, 38.
[Sidenote: LEPIDODENDRON.]
Lepidodendron (_scaly-tree_). _Lign. 39._--Stems cylindrical, covered
towards their extremities with simple, linear, or lanceolate leaves,
which are attached to elevated rhomboidal spaces, or papillæ; papillæ
marked in the upper part with a large transverse triangular scar; lower
part of the stem destitute of leaves.
[Illustration: Lign. 39.
Fig. 1.--A terminal Branch of a Lepidodendron; _nat._
2.--Leaf-scars on the stem of a Lepidodendron; _nat._
_In Coal-shale, Newcastle._]
The remains of this tribe of plants abound in the coal formation, and
rival in number and magnitude the Calamites and Sigillariæ previously
described. These trees have received the name of _Lepidodendra_, from
the scaly character of their stems, occasioned by the angular scars
left by the separation of the foliage, as is the case in arborescent
ferns: the term, however, simply indicates the appearance, for the
surface is not imbricated. Some of these trees have been found almost
entire, from the roots to their topmost branches. One specimen, forty
feet high, and thirteen feet in diameter at the base, divided towards
the summit into fifteen or twenty branches, was discovered in the
Jarrow coal-mine.[105] The foliage consists of simple, linear leaves,
spirally arranged around the stem, and appears to have been shed from
the base of the tree with age. The scars produced by the attachment of
the petioles were persistent; and the twigs and branches are generally
found covered with foliage, as in _Lign. 39_. The roots are Stigmariæ,
like those of the Sigillariæ, as proved by specimens in the Pictou
coal-field, discovered by Mr. Brown.[106]
[105] Wond, p. 722. This specimen is figured and described in Foss. Flor.
[106] Petrifactions, p. 39.
The internal organization of the stem of Lepidodendron differs from
that of Sigillaria, in the absence of the woody cylinder and medullary
rays which constitute so peculiar and important a character in the
latter. The Lepidodendra have only an eccentric, vascular, medullary
zone, the interval between which and the bark is filled up by cellular
tissue.[107] In their structure, external configuration, mode of
ramification, and disposition of the leaves, they accord so closely
with the _Lycopodiaceæ_, that, notwithstanding the disparity in
size, M. Brongniart, Dr. Joseph Hooker, and other eminent botanists,
concur in regarding them as gigantic arborescent club-mosses[108] The
living species of Lycopodiaceæ amount to nearly two hundred, the
greater number of which, like the arborescent ferns, inhabit the
islands of intertropical regions. They are diminutive plants, with
delicate foliage, none exceeding three feet in height; most of them
trail on the ground, but there are a few erect species, one of which
(_Lycopodium densum_) is abundant in New Zealand.
[107] See M. Ad. Brongniart, Archives du Museum d'Hist. Nat. torn. i.
(for 1839), pl. XXX.
[108] Figures of Lepidodendra in _Wond._ p. 718. Pict. Atlas, pl. i.
iii. ix. xxvi. xxvii. xxxiii.
The fruit of the Club-mosses is an oval or cylindrical cone, which
in some species is situated at the extremity of the branches, and
constitutes an imbricated spike. Now associated with the stems of the
Lepidodendra, and very often in masses of their foliage, and in some
instances attached to the extremities of the branches, are numerous
oblong, or sub-cylindrical, scaly cones, garnished with leaves. These
have received the names of _Lepidostrobi_ (scaly-cones), and are
unquestionably the fruit of the trees with which they are imbedded.
[Sidenote: LEPIDOSTROBUS.]
Lepidostrobus. _Lign. 40._--A cylindrical strobilus or cone, imbricated
from above downwards, composed of winged scales, terminating in
rhomboidal discs: the axis traversed by a longitudinal cavity or
receptacle.
These fossils have long been known to collectors, and are figured by
Martin (_Petrif._ _Derbiensia_), Parkinson (_Org. Rem._ vol. i. pl.
ix.), and others. They are cylindrical imbricated bodies, rounded at
both extremities, from two to six or seven inches in length, and one
or two inches in circumference. When broken asunder, a cylindrical
cavity is exposed, which is sometimes hollow, but commonly filled
with mineral matter; and when specimens are found imbedded in shale,
the cone is fringed with linear-lanceolate bracteæ, as in _Lign. 40,
fig. 3_. These fruits, like the fronds of ferns, often form the nuclei
of ironstone nodules, and the leaves are frequently replaced either
by a white hydrate of alumine, or by the mineral called galena, or
sulphuret of lead, and the receptacles filled with the same substances.
The specimens from Coalbrook Dale are generally in this state of
mineralization, and possess great brilliancy; they are interesting
examples of the electro-chemical changes which these fruits of the
carboniferous forests have undergone.[109]
[109] These fossil cones are not liable to decompose, like the pyritous
fruits from the Isle of Sheppey; they require no preparation for the
cabinet; washing injures their lustre; a soft brush will safely remove
any extraneous matter. There is a fine collection of Lepidostrobi in
the British Museum; see Petrifactions, p. 42.
[Illustration: Lign. 40. Lepidostrobi, the fruit of Lepidodendra; _nat._
_Coalbrook Dale._
Fig. 1.--A portion of a cone, showing the imbricated structure and
internal cavity.
2.--The upper part of a cone, displaying the imbricated surface.
3.--A young specimen attached to the extremity of a branch.
]
The figures in _Lign. 40_, represent the usual characters of these
fruits. Of the young specimen, (_fig. 3_,) situated at the termination
of a branch, M. Brongniart observes, "qu'il est impossible de ne pas
reconnaître pour un Lepidostrobus jeune, fixé à l'extrémité d'un
rameau."[110] As it is only in their young state that the spikes are
found attached to the branches, it is probable they were shed as soon
as they arrived at maturity.
[110] Hist. Vég. Foss. tom. ii. p. 47.
_Triplosporite._--Additional light has recently been thrown on the
structure of the Lepidostrobi, by Dr. Robert Brown's examination of
a silicified specimen of the upper part of a strobilus, in which the
internal organization is beautifully displayed. The reader specially
interested in this department of fossil botany should refer to the
original memoir by the illustrious President of the Linnæan Society,
with the accompanying plates that admirably exhibit the microscopic
analysis of the structure of this remarkable fossil; a slice of which
was shown me some years since by the late Marquis of Northampton.[111]
The external surface of the specimen is covered with hexagonal areolæ;
the transverse sections exhibit the appearance of the bracteæ and
sporangia. The strobilus is formed of a central axis of relatively
small diameter, from which proceed bracteæ, about thirteen in number,
that are densely approximated, and much imbricated; and of an equal
number of sporangia, filled with innumerable microscopic sporules,
originally connected in threes. This triple composition of sporules
(which differs from the constant quadruple union in the tribes of
existing plants presumed to be most nearly allied to the fossil,
namely the _Ophioglosseæ_ and _Lycopodiaceæ_) is expressed by the name
_Triplosporite_, adopted by Dr. Brown to indicate this peculiarity of
structure, and the class or primary division to which the original
plant is supposed to belong.[112]
[111] The specimen brought to England was but two inches of the upper
end of the cone; it was purchased conjointly by Lord Northampton, Dr.
Brown, and the British Museum, for 30_l._!
[112] See Trans. Linnæan Society of London, vol. xx. p. 469.
Lycopodites.--Species of true Lycopodiaceæ occur in tertiary marls; a
beautiful specimen, from Germany, _Lycopodites_ _Benettiæ_, is figured
_Wond._ p. 723.
[Sidenote: HALONIA. KNORRIA.]
Halonia; Knorria. _Lign. 41._--Associated with the plants already
described from the coal-measures, there are trunks and branches of
other trees, presenting peculiar and but imperfectly known characters,
which it will be convenient to notice in this place. Fragments of these
stems are to be seen in most public collections of the carboniferous
flora, and should be examined by the student, for figures and
descriptions can convey but an imperfect idea of their nature.
* * * * *
Mr. Denny, the intelligent and indefatigable Curator of the Leeds
Philosophical Society, has given the following admirable summary of the
distinctive characters of the stems of most frequent occurrence in the
Coal,[113] which will be found a useful guide to the collector.
[113] On the Fossil Flora of the Carboniferous Epoch, with especial
reference to the Yorkshire Coal-field. By Mr. Henry Denny, A.L.S.
Proceedings of the Polytechnic Society of Yorkshire; for 1850.
1. _Sigillaria._--Stem furrowed, not branched, leaf-scars small, round,
much narrower than the ridges of the stem.
2. _Favularia._--Stem furrowed, not branched, leaf-scars small, square,
and as broad as the ridges of the stem.
3. _Lepidodendron._--Stem not furrowed, branched, covered with
lozenge-shaped scars in quincuncial order, each having a papilla in
the upper part; the upper portion of the stem and branches with simple
linear leaves; the lower portion destitute of leaves.
4. _Halonia._--Stem not furrowed, branched, covered with indistinct
rhomboidal marks, and tubercular projections disposed in quincunx.
5. _Knorria._--Stem not furrowed, branched, marked with projecting
scars of petioles disposed spirally.
6. _Megaphyton._--Stem dotted, neither furrowed nor branched,
leaf-scars very large, of a horse-shoe figure.[114]
[114] Pictorial Atlas, pl. xxv.
7. _Bothrodendron._--Stem pitted, neither furrowed nor branched, scars
of cones (?) obliquely oval.
8. _Ulodendron._--Stem neither furrowed nor branched, covered with
rhomboidal marks; scars of cones (?) circular.
The characters of the roots called Stigmariæ (_ante_, p. 134), and
of the stems named _Calamities_ (ante, p. 107), and _Equisetites_
(_ante_, p. 106), are sufficiently distinct from the above to be easily
recognized, I will briefly notice those not previously described.
[Illustration: Lign. 41. Stems from the Coal Formation.
Fig. 1.--Halonia regularis. _Coalbrook Dale._
2.--Knorria Taxina. _Roof of the High-main Coal seam, Jarrow
Colliery._ (_Brit. Foss. Flor._)
]
_Halonia._--The specimens usually seen are mere sandstone casts
having a thin carbonaceous crust; the stem is branched and beset
with large elevated knobs, or subcortical protuberances, as shown in
_fig. 1, Lign. 41_. These plants appear to be closely related to the
Lepidodendra; their mode of branching is shown in a beautiful specimen
(in the museum of the Leeds Philos. Soc.) figured and described by Mr.
Denny, which is also remarkable because it indicates the probability
that the Haloniæ, and the fossil stems, termed Knorriæ, are identical;
for the specimen in question, which in its branches is unquestionably
of the former type, has the base of the stem impressed with the
leaf-scars of the latter.
_Knorria._--To this genus the authors of the Fossil Flora of Great
Britain referred those stems which have projecting leaf-scars, arranged
spirally. The beautiful specimen figured as _Knorria taxina_, _Lign.
41, fig. 2_, closely resembles a young branch of Yew (_Taxus_), and
perhaps might be more correctly named _Taxites_.
_Bothrodendron and Ulodendron._--These genera, together with
_Megaphyton_, are stems of a very remarkable character, and are easily
distinguished by the vertical rows of large and distant scars. The two
first have two series of very deep oval depressions on opposite sides
of the stems, arranged alternately in the specimens I have examined:
from the size and form of these obliquely-oval cavities, it is supposed
that they were formed by the attachment of cones, and not by petioles;
but their real nature is involved in obscurity.[115]
[115] Figured in Bd. pl. lvi.
In _Megaphyton_, the large ovate scars indicate the attachment of
deciduous branches or gigantic leaves, which did not grow all round the
stem, but in a regular order of superposition on each side.[116]
[116] Figured in Pict. Atlas, pl. xxv.
[Sidenote: ASTEROPHYLLITES.]
Asterophyllites.--I shall conclude this notice of some of the most
characteristic trees of the Carboniferous Flora, with an account of a
tribe of plants whose remains are so common in the coal-shales and
grits, that there are but few large slabs with vegetable remains that
do not exhibit examples of the elegant verticillate foliage of one or
more species. The term _Asterophyllites_, (expressive of the star-like
form of the leaves,) applied to this family by M. Ad. Brongniart,
includes several fossil plants which are known to geologists under
different generic names; the following concise account may be useful to
the student.[117]
[117] Consult _Tableau des Genres de Végétaux Fossiles_, par M. Ad.
Brongniart. Diet. d'Hist. Nat. Paris, 1849.
1. _Calamodendron._--These are arborescent stems, ligneous internally,
and covered with a smooth carbonaceous crust, without regular
longitudinal striæ, and not articulated; but the woody axis covered
by this bark is deeply striated and articulated, resembling in this
respect the true Calamites. These stems have a large central pith,
or medullary column, surrounded by a ligneous zone, which is formed
of radiated bands, without circles of growth: the structure of the
carbonized bark is unknown.
2. _Asterophyllites._--These are supposed to be the branches and
foliage of the stems above described.
3. _Sphenophyllum._--Plants, differing in the form of the leaves,
but analogous in structure and mode of fructification to the
Asterophyllites.
4. _Annularia._--Herbaceous aquatic plants, distinct from the preceding.
5. _Volkmannia._--These fossil plants are Asterophyllites in
fructification.
The _Asterophyllites_ (_Lign. 42_) had branched articulated stems,
with verticillate leaves, arranged perpendicularly to the branches
which supported them: but as the foliage is in most instances partially
concealed, the natural form is but seldom observable.
The original plants are supposed to have been a tribe of flowering
dicotyledons, for small seed-vessels resembling those of the Cypress
are often found with the foliage.
[Illustration: Lign. 42.
Asterophyllites equisetiformis; _nat._
_Coal-shale._ (_Foss. Flor._)]
[Sidenote: ANNULARIA CARDIOCARPON.]
The _Annulariæ_ were herbaceous plants with verticillate foliage
like the former, but the whorls were arranged on the same plane with
the stems on which they grew, and their remains have a very elegant
appearance when expanded in the coal schists. It is supposed that they
were aquatic plants, and that the stems and leaves floated on the
surface of the water.[118]
[118] _Wond._ p. 717. Petrifactions, pp. 27, 43, &c. For coloured
figures see Pictorial Atlas, pl. v.
Sphenophyllum (_wedge-shaped leaf_). _Lign. 43._--The fossil vegetables
thus named, though somewhat resembling in their elegant verticillate
foliage the Asterophyllites, differ essentially, and are regarded by
M. Brongniart as herbaceous plants related to the _Marsiliaceæ_, or
Pepper-worts. The leaves are triangular, truncated at the summit, and
very deeply lobed and dentated. The fructification consists of sessile
axillary or terminal spikes, composed of verticillate bracteæ, covering
the receptacles. This mode of fructification resembles that of the
Asterophyllites.[119]
[119] For details consult _Tab. des Genres de Vég. Foss._ p. 52.
Cardiocarpon.--_Lign. 44. fig. 1._--These are small fossil fruits or
seed-vessels, which much resemble those of the Thuja or _Arbor-vitæ_,
and are so often found imbedded with masses of the foliage of
Asterophyllites, that it is conjectured they belong to those plants.
They occur in groups of from five to twenty, and evidently were
_didymous_, _i.e._ grew in pairs. _Fig. 1a_. is an enlarged view, to
show the surface left by the attachment of the twin-seed.
[Illustration: Lign. 43.
Fig. 1.--Sphenophyllum Schlotheimii; _nat._
2.--Sphenophyllum erosum.
_Coal-Shale._]
Trigonocarpum. _Lign. 44. figs. 3. 4._--These fruits, which resemble
those of certain Palms, are often met with in the coal-mines of
Leicestershire and Yorkshire; frequently occurring in groups of thirty
or forty, as if they were the scattered seeds of a raceme of a Palm:
they are referred to the genus Nœggerathia, a tree of the carboniferous
formation allied to the Palms.
[Sidenote: FOSSIL FRUITS.]
A figure of a fossil fruit from the Oolite--Carpolithes Bucklandi, is
introduced in _Lign. 44, fig. 2_, and will be described hereafter.
[Illustration: Lign. 44. Fossil Fruits, or Seed-vessels; _nat._
Fig. 1.--Cardiocarpon acutum. _Snibstone Coal-mine, Leicestershire._
1_a_.--One of the above magnified.
2.--Carpolithes Bucklandii. _Coralline Oolite, Malton._
3.--Trigonocarpum olivæforme. _Snibstone Colliery._
4.--Trigonocarpum Nöggerathi.
]
The reader will observe that the fossil vegetables hitherto described
belong, with but few exceptions, to the Carboniferous flora; and that
the remains of Ferns, Calamites, Sigillariæ, and Lepidodendra, compose
in a great measure those prodigious accumulations of mineral fuel, or
coal, which supply the luxuries and necessities created by civilization.
Our review of fossil plants will now assume somewhat of a botanical
arrangement, and we proceed to notice some of the most characteristic
vegetable forms of the secondary and tertiary formations. We commence
our examination with those remarkable tribes of gymnosperms, the
Cycadaceæ, which comprise the Zamiæ and Cycadeæ.
Fossil Cycadaceæ.
The plants of this subdivision of the vegetable kingdom, from their
singular structure and mode of growth, their simple cylindrical stems,
and coronets of pinnated foliage, resembling that of certain palms,
their usually gyrate vernation like that of the ferns, and their
anomalous inflorescence and fructification, are objects of great
interest to the scientific botanist; while the abundance of their
fossil remains in the secondary formations renders them of the highest
importance to the geologist.
[Illustration: Lign. 45.
Foliage and upper part of the Stem of Cycas revoluta 1/12 _nat._
_In Kew Conservatory._]
As many kinds of Zamia[120] and Cycas are cultivated in our hot-houses,
the general appearance of the plants of this order must be familiar to
the reader: the annexed figure of a beautiful living Cycas in the Royal
Gardens at Kew, will serve to illustrate the general aspect of these
exotics.
[120] The Linnæan genus Zamia is now separated into five or six genera,
as Encephalartos, Macrozamia, Dion, &c.
The Zamiæ are short plants, with stout cylindrical stems, beset
with thick scales, which are the bases of the petioles that have
been shed: towards the summit the stem is garnished with a crown of
elegant leaves; the fruit resembles the cones of pines. The leaves
are pinnated, and very tough; their venation is either parallel as
in endogens, or dichotomous as in ferns, but never reticulated as in
exogens: in a young state they are coiled up like a crosier, as in
ferns.
The Cycadeæ have the general aspect of the Zamiæ, but differ in their
fructification and other characters; and some species have the stem
bifurcated towards the top, and attain a height of upwards of twenty
feet; for example, _C. circinalis_.
The stem in its internal structure[121] bears a close analogy to that
of the Coniferæ; it has a central medullary column surrounded by a
ligneous cylinder, divided by cellular medullary rays, each composed
of bundles of vessels, and a thick cellular cortical investment or
false-bark,[122] composed of the persistent scales that formed the bases
of the petioles. (See _Pl. V. fig. 5._)
[121] See _Bd._ pl. lxii.
[122] See _Bd._ vol. i. pp. 494-498, for detailed description of
structure in recent and fossil Zamiæ and Cycadeæ.
The existing species of Cycadaceæ are exclusively natives of hot
regions, and chiefly inhabit the West Indies, South Africa, Equinoctial
America, Japan, New Holland, &c.; not one species is known in Europe: a
fact in striking contrast with the abundance of fossil plants of this
order, which occur throughout the secondary formations of England and
the continent.[123]
[123] The most interesting collection of living Cycadeæ and Zamiæ near
London, is that of James Yates, Esq., of Lauderdale House, Highgate; it
comprises choice examples of several of the sub-genera into which these
plants are now divided by botanists.
No true cycads have hitherto been discovered in the carboniferous
deposits; it is in the floras of the secondary epochs, from the new
Red to the Cretaceous inclusive, that this tribe of plants forms an
important feature. The foliage, stems, and fruits, occur in a fossil
state; and as these organs cannot be referred with certainty to their
respective plants, distinct genera are formed for their reception.
_Foliage._--From the tough and durable nature of the leaves, the
foliage of the Cycadeæ occurs in a fine state of preservation; and in
the fluvio-marine deposits of the Oolite of Yorkshire, many specimens
of great beauty have been collected. I know not another locality in
England so rich in fossils of this kind, as the cliffs along the coast
near Scarborough; Gristhorpe Bay is well known to collectors. Not only
the leaves, but also the fruits or cones occur, and of these, examples
are to be seen in most public museums.[124] The leaves are carbonized,
but the venation is well preserved.
[124] British Museum: see Petrifactions, p. 54, Room 1, Case F.
[Illustration: Lign. 46. Part of a leaf of Pterophyllum comptum; _nat._
_Oolite, Scarborough._]
The leaflet of the recent Cycas is distinguished by a strong nervure,
which runs along the middle; that of Zamia has no midrib, but fine
parallel veins that pass direct to the margin.
Pterophyllum comptum. _Lign. 46._--The general aspect of these
fossils is shown in this figure of a leaf, referred to the genus
_Pterophyllum_, which is characterized by leaflets, often slightly
united at their base, truncated at the summit, of a quadrangular or
oblong form, and having fine, straight, parallel veins. The leaves are
ten or twelve inches long, and have fine lanceolate leaflets; they are
abundant in the same beds, and are often associated with the cones or
fruit[125] figured in _Lign. 48_.
[125] Brit. Mus. Petrifactions, p. 55.
[Sidenote: ZAMITES PECTINATUS.]
Zamites pectinatus. _Lign. 47._--In the Stonesfield slate, collocated
with remains of reptiles, fishes, insects, and mollusks, leaves and
fruits of cycads are occasionally met with. A portion of a leaf nine
inches long is here figured. The Lias of Dorsetshire has yielded many
beautiful relics of this family[126]
[126] In the carboniferous strata of Eastern Virginia, United States,
which are referred by Professor Rogers to the Oolitic epoch, leaves of
Cycadeous plants are abundant. See Trans. American Geol p. 298.
[Illustration: Lign. 47. Part of a leaf of Zamites pectinatus; _nat._
_Oolite, Stonesfield._]
But few vestiges of the foliage of Cycads have been observed in
the Wealden formation of England; one elegant leaf, however, of an
undescribed species, was obtained some years since, from a sandstone
quarry in Surrey, and is figured in my Geology of the South-east of
England, p. 238; it is named in honour of my distinguished friend, M.
Ad. Brongniart, _Cycadites Brongniarti_. The Wealden of the north of
Germany is very rich in fossil Cycadeæ; my friend. Dr. Dunker, has
figured and described twelve species in his admirable work on the
organic remains of that formation.[127]
[127] Mon. Norddeutschen Weald, tab. i. to vii.
_Fruits._--The cones or fruits which occur with the foliage of Zamiæ
in the carbonaceous shales and marls of the Oolite of the Yorkshire
coast, are very fine, and have been described under the various names
of _Zamites Mantelli_, _Z. gigas_, and _Z. lanceolatus_.
An interesting memoir on the structure of these fossils, by James
Yates, Esq. (a gentleman distinguished for his knowledge of the
recent Cycadaceæ), is published in the Proceedings of the Yorkshire
Philosophical Society for 1849, p. 37; and another communication on
the same subject by my friend Professor Williamson, of Manchester, in
_York. Phil. Trans._ 1819, p. 45; to these papers I must refer for
a detailed account of all that is at present known respecting their
organization.
[Illustration: Lign. 48. Fruit of Zamites Mantelli, (_Brongniart_);
_nat._
_From near Scarborough._
The surface of the cone is concealed by the bracteæ.]
Zamites Mantelli.[128] _Lign. 48._--The leaves associated with the fruit
here figured, have lanceolate leaflets that insensibly contract at the
base, and are inserted obliquely into the rachis; thus resembling
the foliage of the recent _Encephalartos_. With these leaves, and the
ovate cones (_Lign. 48_), are occasionally found a circle of leaves
or elongated scales, locally termed "_collars_," which Professor
Williamson has shown to be a zone formed by a scaly bud in which the
germ of the plants was inclosed. In the progress of development, the
fruit burst through the upper part of the investing sheath, and, as it
grew to maturity, rose above the incurved elongated bracteæ, till the
latter formed a zone or "collar" around the pedicle of the cone.[129]
These fossils have been mistaken for flowers.[130]
[128] _Podozamites_ of Braun.
[129] Proc. Yorkshire Philos. Soc. 1849, p. 45.
[130] Bird's Yorkshire, tab. i. figs. 1 and 7.
It does not appear that the structure of the cone has been preserved
in any of the specimens, so as to demonstrate the characters of the
original; in all those I have examined, the surface of the fruit is
concealed by the elongated bracteæ, which are pressed flat, and adhere
so firmly to the inclosed body, as to render it impossible to ascertain
its nature.[131] Mr. Williamson is of opinion that the plant resembled
the recent _Cycas circinalis_, in its great height, and lax habits; and
states, that he had seen portions of leaves that were three feet in
length.
[131] Brit. Mus. Petrif. p. 55.
Zamites crassus. _Lign. 49, fig. 1._--In Sandown Bay, on the south
coast of the Isle of Wight, where the Wealden beds rise to the surface
from beneath the lowest strata of Greensand on the east and west,
several cones have been found, associated with other vegetable remains,
and bones of the Iguanodon, &c. A fossil cone from this locality is
here figured; it bears considerable resemblance to the fruit of the
recent _Encephalartos_.
[Sidenote: ZAMITES OVATUS.]
Zamites ovatus. _Lign. 49, fig. 2._--A few examples of cycadeous
fruits have been collected from the Greensand of Kent and Sussex. The
beautiful fossil represented, _Lign. 49, fig. 2_, from Foss. Flor.
is referred to the Zamiæ, by the eminent authors of that work; but it
presents in its imbricated character a greater analogy to a pine cone.
[Illustration: Lign. 49. Fossil Fruits of Cycadeous Plants; 1/2 _nat._
Fig. 1.--Zamites Crassus. _Wealden, Isle of Wight._
2.--Zamites Ovatus. _Greensand, Kent._
]
Zamites Sussexiensis.--At Willingdon, near Eastbourn, in Sussex, a cone
nearly six inches long was discovered in a bed of Greensand, which
abounds in fossil coniferous wood: it is of an elongated cylindrical
form, and covered with hexagonal scales. I have provisionally named
it _Zamites Sussexiensis_ (Geol. Proc. 1843), as it presents a nearer
resemblance to the fruit of Zamiæ than to that of Conifers.
Trunks and Stems of Cycadaceæ.--In this section I shall notice the
fossil plants which occur so abundantly in the fresh-water deposits
that overlie the marine oolitic limestone of the Isle of Portland, and
which must be familiar to my readers, from the graphic account of the
circumstances under which they occur, by Mr. Webster, and subsequently
by Dr. Buckland, and Sir H. De la Beche. In my Wonders of Geology,
p. 387, and Geol. Isle of Wight, p. 395, the geological phenomena of
that most interesting locality, the Isle of Portland, are so fully
described, that it will not be necessary to dwell upon them; the
structure and affinities of the fossil vegetables are the especial
objects of our present inquiry.
[Sidenote: MANTELLIA NIDIFORMIS.]
[Illustration: Lign. 50. Silicified Trunk of Mantellia nidiformis
(_Brongn._); 1/4 _nat._
(_Cycadites megalophyllus._ _Bd._)
_Wealden. Isle of Portland._
_a._ Central mass of cellular tissue, _b._ Circle of ligneous plates,
_c._ Zone of cellular tissue, _d._ False-bark.]
Mantellia. _Lign. 50, 51._--The fossil Cycadeæ of the Isle of Portland
were first described botanically by Dr. Buckland, (Geol. Trans, vol.
ii. 2d Series,) under the name of _Cycadeoidea_; of which Memoir the
account in _Bd._ p. 404, is an abstract. M. Ad. Brongniart, considering
these plants as a peculiar type, referred them to a new genus, which he
did me the honour to name _Mantellia_ (_Prod. Veg. Foss._). These stems
or trunks are from one to two feet in height; the circumference of the
largest not exceeding three feet. The stem is subcylindrical, and
the external surface covered with the rhomboidal scars formed by the
attachment of the leaf-stalks, and which are widest in their transverse
diameter.
There are two species, which are readily distinguished by the form of
the stems, and the difference in the size of the cicatrices left by the
petioles.
The most common kind is short, and spheroidal, and the leaf-scars are
relatively large; its shape has caused it to be named "_Crows' nest_,"
by the quarrymen, who believe these plants to be nests that were built
by crows in the trees of the petrified forest with which they are
imbedded. The specific name (_nidiformis_) adopted by M. Brongniart,
expresses this popular notion.
_Lign. 50._ represents a fine example from the Portland Dirt-bed, which
exhibits a structure altogether similar to that which characterizes
the stems of recent cycadeous plants; namely, (_a_) a central mass of
cellular tissue surrounded by circles of laminated ligneous rays or
plates (_b_); then a zone of cellular tissue (_c_), and an external
cylinder of false-bark (_d_). The mode of increase by buds, from
germs in the axillæ of the petioles, as in the living plants, is also
distinctly seen.
[Illustration: Lign. 51. Mantellia cylindrica.
(_Brongn._); 1/8 _nat._
(_Cycadites microphyllus. Bd._)
_Wealden. Petrified Forest of the Isle of Portland._]
The other species is subcylindrical, and the leaf-scars are much
smaller and more regular than in _M. nidiformis_, indicating a more
delicate foliage, as expressed by Buckland's specific name: that of M.
Brongniart refers to the cylindrical form of the stem. This plant was
higher and more slender than its associate. Numerous buds are seen in
the axillæ of the petioles in the specimen figured.
These fossils present, both externally and internally, a close relation
to the bulbiform stems of the recent Cycadeæ, named _Encephalartos_, of
South Africa.[132]
[132] The fossil Cycads of the Isle of Portland are admirably described
and illustrated in Dr. Buckland's Bridgewater Essay, (p. 497, and pl.
lx. lxi.), and their internal structure is fully explained.
Neither the leaves nor the fruit are known: a cone found in the
Dirt-bed of Portland, and attributed to these plants, appears to belong
to the coniferæ of the petrified forest. Examples of Mantelliæ have
been found in the quarry of Portland-stone at Swindon, Wilts.
[Sidenote: CLATHRARIA LYELLII.]
[Illustration: Lign. 52. Clathraria Lyellii.
_Wealden._
A branched example of the inner axis: the original 3-1/2 feet high.]
Clathraria[133] Lyellii. _Lign. 52-57._--The fossil plants to which I
would next direct attention were first discovered by me in the Wealden
strata of Sussex, in 1820, and were figured and described under the
name they still bear, in my Fossils of Tilgate Forest, in 1827. The
specimens figured in that work are the most illustrative hitherto
discovered, with but one exception.[134]
[133] EC C
lathraria, _i.e._ _lattice stem_, from the scars left by the
petioles.
[134] They are now in the British Museum; see Petrifactions, p. 45.
_Room_ I. _Case_ E.
From the imperfect state of the remains of these plants, the structure
and affinities of the originals were very ambiguous, and the fossils
have been placed by some eminent botanists with the Liliaceæ, and by
others with the Asphodeleæ; their true botanical position is doubtless
with the Cycadaceæ; for in some points they resemble the Zamiæ, in
others the Cycadeæ.
The stem of the Clathraria is composed of a solid internal axis, the
surface of which is covered with reticulated fibres; the large branched
specimen of this part, figured in _Lign. 52_, is the finest example
hitherto obtained: it was discovered, with bones of the Iguanodon,
in a quarry near Cuckfield, Sussex, in 1820. The axis is invested
with a very thick false-bark, formed of the consolidated bases of the
leaf-stalks, the insertions of which are rhomboidal and transverse.
The outer surface of the bark is consequently marked with elevated
lozenge-shaped cicatrices (_Lign. 53_), separated from each other by a
marginal furrow, which is surrounded by a parallel ridge or band of a
fibrous structure.
[Illustration: Lign. 53. Clathraria Lyellii.
1/4 _nat._
A stem, with rhomboidal transverse scars, left by the petioles; broken
transversely and separated, to show the internal axis at _a_, which,
if the pieces were united, would be received in the cavity below the
depression, or cicatrix, on the middle of the upper portion, _b_, was
probably the situation of a resinous secretion, like the dragon-blood
in the Dracæna.]
The cortical zone is generally converted into a cylinder of stone,
which in some examples separates from the axis. In a beautiful specimen
of this kind, _Lign. 54_, the axis projects and is surrounded by the
false-bark.
The axis is solid, and has its surface strongly marked with interrupted
ridges. This surface has generally patches of vascular tissue adhering
to it; and there are here and there deep pits, or lacunæ, which
probably contained a resinous secretion. Thin transverse sections
of the axis, prepared with Canada balsam, and examined under the
microscope, only give faint traces of cellular tissue.
[Illustration: Lign. 54.
Clathraria Lyellii; 1/4 _nat._
_Wealden Sandstone._
_Tilgate Forest._
Portion of a stem, scored by the cicatrices of the petioles; showing
the Axis _a_, surrounded by the cortical cylinder.]
I have spared neither trouble nor expense in endeavouring to detect
the organization of this plant; numerous sections of stems have been
cut, and examined microscopically, but very few exhibit any traces of
structure; and in those which retain some vestiges of organization,
the siliceous mass which permeates the vascular tissue, is not
sufficiently transparent to yield satisfactory results. It can only
be inferred that in their internal organization, as in their external
characters, the Clathrariæ were most nearly allied to the Cycadeæ or
Zamiæ. A remarkable specimen, (_Lign. 56_,) discovered in a stratum of
Chalk-marl, near Bonchurch, confirms this view, and throws much light
on the nature and relations of these vegetables.
[Illustration: Lign. 55.
Petiole of Clathraria Lyellii;
_a._ External aspect.
_b._ Inner surface.
_c._ Vascular pits left by the separation of the leaf.
]
This fossil is a portion of the summit of a stem garnished with
persistent petioles, or leaf-stalks; it is fifteen inches in length,
and nearly perfect at the top; and at the lower end, which has been
broken off transversely, the inner axis (_Lign. 56 a_.), surrounded
by the false-bark formed by the confluence and consolidation of the
bases of the petioles, is exposed. The stem has been stript of the
leaf-stalks at the lowermost part, and exhibits the characteristic
lattice-like scars. The petioles are for the most part entire; some of
them are abortive, and others, which have supported leaves, are marked
on the summits with vascular pits, indicating that the foliage was
shed naturally; as shown in _Lign. 55 a_. These petioles were probably
persistent for some years, as in the existing Cycads. The opposite side
of the stem to that represented is covered with elongated and flattened
petioles.
[Illustration: Lign. 56.
Clathraria Lyellii; 1/4 _nat._
_Chalk-marl. Bonchurch, Isle of Wight._
The summit of a stem garnished with petioles; the lower part shows
the cicatrices left by the removal of some of the petioles: _a_, the
internal axis.]
On the sea-shore bounded by cliffs of Wealden rocks, in the Isle of
Wight, water-worn portions of stems of Clathrariæ are occasionally met
with; and these are impressed with the lozenge-shaped areas left by the
petioles, as in the specimen, _Lign. 57_. Mr. Saxby, of Bonchurch, has
favoured me with the loan of a thin section of a stem of Clathraria in
which the bundles of vascular tissue in the petioles appear to be made
up of spiral vessels. From what has been advanced, it is obvious that
these remarkable plants of the Wealden flora were gymnosperms, closely
related to the Cycadeæ.
Vestiges of roots, seed-vessels, and panicles, have been found in the
Wealden, which may possibly belong to the Clathraria; but the evidence
as to their presumed relationship is at present too vague to require
further notice.
[Illustration: Lign. 57.
Clathraria Lyellii; 1/2 _nat._
Specimen, showing the water-worn external surface.]
[Sidenote: ENDOGENITES.]
Endogenites erosa.--(_Geol S. E._ pl. i.; Tilg. Foss. pl. iii.; and by
Dr. Fitton in _Geol. Trans._ vol. iv.)--The genus _Endogenites_ was
established by M. Ad. Brongniart for the reception of those fossil
stems and woods, whose internal structure is endogenous, but which are
too imperfect to be referred to any particular family. In this category
must be placed certain silicified stems having a carbonaceous cortical
investment, which I discovered in the strata of Tilgate Forest, in 1820.
These fossils often occur in the layers of lignite which traverse the
clay-beds in some parts of the Weald of Sussex. They are from one to
eight inches in diameter, and five or six feet in length, and of very
irregular shapes; I have not observed any indications of branches.
Some specimens are subcylindrical in the middle, and gradually taper
to a point at each end; others are of a depressed clavated form, like
some of the Cacteæ or Euphorbiaceæ. They are generally silicified,
and, when _in situ_, are invested with a friable carbonaceous crust,
of a glossy lustre, which soon falls to pieces on exposure to the
atmosphere, so that cabinet specimens seldom retain any vestiges of it.
When this coaly matter is removed, the surface of the silicified stem
is seen to be traversed by numerous fine meandering grooves, and deep,
tortuous channels, disposed in an irregular manner, in a longitudinal
direction. These channels or vessels, which are generally lined
with quartz crystals, give the surface that eroded appearance which
suggested the specific name, erosa; but this term is inapplicable,
for the perforations and sinuosities are not the effect of erosion,
but result from the structure of the original. Polished sections,
seen by transmitted light, are represented in Dr. Fitton's memoir
(_Geol. Trans._ vol. iv.); and I have had many slices ground as thin
as possible, in the hope of detecting the characters of the vascular
tissue. In one example there are indications of a cycadeous structure,
which favour the conclusion, that the originals belonged to an extinct
tribe of gymnosperms; but in other specimens, bundles of vascular
tissue, resembling those of palms, are apparent.
Large water-worn stems of _Endogenites_ are occasionally washed out of
the Wealden cliffs at Hastings, and in Sandown and Brook Bays, in the
Isle of Wight.
[Sidenote: FOSSIL CONIFERÆ.]
Fossil coniferæ.
The other great natural order of Gymnospermous phanerogamiæ,[135] the
_Coniferæ_, or cone-bearing--so named from the form of their fruit, of
which the fir-cones and larch-juli are familiar examples,--comprise the
extensive tribes of Firs and Pines, and the Cypresses, Yews, Junipers,
Cedars, &c., among which are the loftiest trees on the face of the
globe.
[135] Signifying, flowering plants with naked seeds.
The Conifers are all arborescent, having numerous branches, which are
in general disposed with much regularity. The leaves are commonly
acicular or needle-shaped, narrow, and linear: in two or three genera,
however, (_Dammara_, _Podocarpus_,) the foliage departs remarkably from
the ordinary type, the leaves being broad and flat. The structure of
the stem, though in its general characters essentially exogenous (see
_Plate IV. fig. 4_),--that is, having a central pith, medullary rays,
zones of vascular tissue, and concentric circles of growth,--differs
in the almost entire absence of spiral vessels, and in the peculiar
modification of the radiating bands of woody fibre, which are made up
of uniform longitudinal vessels, and run parallel with the medullary
rays. The lateral walls of these vessels have longitudinal rows of
areolæ, which are generally circular or elliptical, but when in contact
are angular and polygonal: each areola has a small pore or punctation
in the centre. These discs, glands, or ducts, as they are called, are
variously arranged in different genera; they are generally confined to
the contiguous and corresponding lateral surfaces of the fibres; and
occur rarely, if ever, on the inner and outer aspects of the vessels.
In the recent genus Pinus the rows of ducts are single in some species;
in others both single and double series occur, but never more than two,
and in the latter case the ducts are always parallel to each other (see
pl. v. 3_b_. _Wond._ pp. 696, 725). But in the _Araucariæ_, or Norfolk
Island Pines, the vessels have double, triple, and sometimes quadruple,
rows of discs, of smaller size than in the common pines; and in the
double series, these bodies are always arranged alternately (_Wond._ p.
696. _Bd._ 56 _a_.); Mr. Nicol states that there are about 50 discs in
the length of 1/20 inch, the diameter of each not exceeding 1/1000 inch.
The form and arrangement of these ducts, and the structure of the
medullary rays, are the characters on which the scientific botanist
relies for the detection of the affinities of the coniferous trees,
whose mineralized trunks and branches, in a fragmentary state, are, for
the most part, the only relics of these important tribes of the lost
floras of the earlier ages of our planet.[136]
[136] I know not a more delightful and instructive branch of science for
the young and inquiring of both sexes, than this department of Fossil
Botany, which the recent improvements in the microscope have rendered
so accessible; and yet there are but few cultivators of fossil botany
in England!
The great value of these data will be shown in the sequel.
* * * * *
The stems, fruit, and foliage, of Coniferæ, occur in the various
fossiliferous deposits, from those containing the earliest traces of
terrestrial vegetation to the newest tertiary strata; and a large
proportion of the petrified wood found in the British formations
belongs to trees of this order. The presence of rows of ducts on the
ligneous fibres, which is peculiar to this division of gymnosperms,
as we have already explained (_ante_, p. 58), is so easily detected
by microscopic examination, that the merest fragment of fossil
coniferous wood retaining internal structure, may without difficulty
be recognized. The number of rows, and the opposite or alternate
arrangement of the areolæ, are characters which, in the living pines
and firs, enable us to refer the respective trees to European or exotic
forms; but in the fossil coniferous wood, much diversity exists in
other not less important points of structure, and for the successful
cultivation of this department of fossil botany, works especially
devoted to the subject must be consulted. To the English student, Mr.
Witham's beautiful volume, "Observations on the Structure of Fossil
Vegetables, Edinburgh, 1831," will be found a valuable guide.
[Sidenote: FOSSIL CONIFEROUS WOOD.]
Fossil Coniferous Wood.--The coniferous wood of the secondary
formations of England, belongs for the most part to the Araucarian
type: that is, the glands, when in double rows, are placed alternately,
as in the Norfolk Island Pines (_Wond._ p. 696), and not side by side,
as in the common European species of firs and pines (_Bd._ p. 486).
Numerous sections of this kind of fossil wood are figured by Mr.
Witham, from specimens obtained from Lennel Braes, on the banks of the
Tweed, near Coldstream; and from near Allanbank Mill, in Berwickshire
(_Obs. Foss. Veg._ p. 14); a fossil trunk, 40 feet long, discovered in
Craigleith Quarry, near Edinburgh, at a depth of 136 feet, possessed
the same structure.
Palæoxylon (_coniferous wood of the Coal Measures_).--The existence of
coniferous trees in the Carboniferous flora, and the fact that their
trunks and branches had contributed to the formation of coal, was first
discovered and clearly demonstrated by Mr. Witham in the work to which
reference has been made. Figures of the peculiar structure observable
in thin slices of coal, are given in _Obs. Foss. Veg._ pl. iii. iv. v.
This carbonized wood resembles that of the Araucariæ in the multiple
series of ducts, and their alternate arrangement; but the presence of
thick compound medullary rays in these stems,--a character unknown in
any living conifers,--led M. Brongniart to place them in a separate
genus--_Palæoxylon_ (ancient wood); characterized by the presence
of medullary rays formed of numerous layers of cells, which are not
arranged in superimposed series, and that present a lanceolate or oval
form, in a section perpendicular to their direction.[137]
[137] The _Pinites Withami_, and _P. medullaris_, of Lindley and Hutton,
figured in Mr. Witham's work, belong to this genus. It may interest the
reader to know that slices of these woods prepared for the microscope
by Mr. Nicol, (presented to me by the late Dr. Henry, of Manchester,)
not only expose the vegetable organization in an admirable manner, but
also form beautiful objects for the exhibition of polarization.
Peuce.--Another species of coniferous wood from the coal is thus named;
it differs from the former in the medullary rays being composed but of
one layer of superposed cells.
Araucarites (_Dadoxylon of Endlechen_).--This term is employed to
designate the fossil wood whose structure is apparently identical
with that of the living species of Araucariæ, having the same kind
of medullary rays, and the ligneous fibres studded with discs or
areolæ, which are polygonal, often hexagonal, and disposed in several
alternating series. This wood is common in the Lias, Oolite, Wealden,
and Chalk.
Drifted fragments of coniferous wood of this type occur in the
Stonesfield slate, associated with leaves and fruits of cycadeæ,
and with marine shells, bones of reptiles, fishes, and mammalia; at
Scarborough, with the ferns and zamiæ previously described; at Swindon,
in the Portland oolite, with belemnites, ammonites, trigoniæ, &c.
[Sidenote: STERNBERGIA.]
Sternbergia.--To the Araucarian tribe, according to the recent
investigations of Professor Williamson, must be referred certain
fossil stems found in the coal-measures, and named _Sternbergiæ_.[138]
These are long solid cylindrical casts of sandstone or clay, with
annular constrictions, which are generally invested with a thin film
of carbonaceous matter; when this crust is removed the surface is
found to be marked with longitudinal ridges. These fossils were once
supposed to be the stems of plants allied to Yucca or Dracæna; but,
as was first shown by Mr. Dawson and Mr. Dawes,[139] they are merely
sandstone casts of the medullary axis or cylinder of an extinct genus
of coniferæ, allied to the Araucariæ: a specimen in which the cast was
surrounded by a thick ligneous cylinder, heaving enabled that acute
observer to detect the structure of the original.[140] The Sternbergiæ
are sandstone casts of central cavities existing within the true pith;
which cavities, under some favourable conditions, were filled with
inorganic materials. Mr. Williamson is inclined to believe that all
the coniferous wood from the coal-measures, belonging to the genus
_Dadoxylon_, is referable to the trees of whose piths the _Sternbergiæ
approximatæ_ are internal casts; and that some of the foliaceous
appendages of these trees have been confounded with Lepidodendra.[141]
[138] See Pictorial Atlas, pl. xviii. p. 53.
[139] On the Coal formation of Nova Scotia, Geol. Proc. 1846.
[140] See Prof. Williamson's Memoir on Sternbergia, Manchester Philos.
Trans. 1851.
[141] Ibid. p. 355.
Petrified Forests of Conifers.--The most remarkable assemblage of
fossil conifers is that presented in the well-known quarries in the
Island of Portland, to which allusion was made when describing the
Mantelliæ obtained from that locality (_ante_, p. 157). Referring to
_Wond._ p. 385,[142] for an account of the geological circumstances
under which the phenomena occur, it will suffice to state that a
forest of pines appears to have been submerged, and the trunks to have
become petrified, whilst standing erect on the spot where they grew;
the Cycads still shoot up as it were between the stems, and the roots
of the trees, though changed into flint, extend into the bed of mould
whence they originally derived support, and which is so little altered
in appearance, as to be called the _Dirt-bed_, by the quarrymen; thus
realizing the fable of the petrified city in Arabian story, whose
inhabitants were turned into stone, in the varied attitudes of life.
[142] Geol. I. of Wight, p. 394. Petrifactions, p. 56.
No foliage has been observed in connexion with these trees; not a leaf
has been found in the rocks: a cone, nearly related to the fruit of
Araucaria excelsa, was discovered in the Dirt-bed.
At Brook-point, in the Isle of Wight, an equally interesting fact may
be observed. At the base of the cliff, which is entirely composed of
Wealden clays, shales, and sandstones, there is a vast accumulation of
petrified firs and pines, imbedded in the indurated grit that forms
the lowermost strata on the sea-shore, and of which the reefs and
rocks, produced by the encroachments of the sea, and that extend far
from land, are composed. These can be examined at low-water, and the
observer, upon lifting up the fuci and algæ which cover them, will
find the rocks and masses of stone to consist of petrified trunks of
coniferæ. There are no erect trees as in Portland; on the contrary, the
stems are prostrate, and lie confusedly intermingled, and associated
with bones of Iguanodons and other reptiles, and large mussel-shells;
the whole presenting the characters of a raft of forest trees which had
drifted down the stream of a vast river, and entangled in its course
the limbs and carcasses of animals that were floating in the water, and
the shells that inhabited the river, and at length became submerged in
the bed of the delta or estuary. Both foliage and fruit have been found
in the Wealden deposits at Brook, and will be described hereafter.[143]
[143] See Geol. I. of Wight, chap. x. and xi.
In the sands of the Desert of Sahara, in Egypt,--among the mammalian
bones of the Sub-Himalayas,--and in the tertiary deposits of Virginia
associated with cycads,--drifted trunks of conifers have been
discovered.
Fossil trees of this family also occur in various localities in
Australia and Van Diemen's Land, the wood of which is in some parts
calcified, and in others silicified. The same trunk often has
externally a white friable calcareous zone, several inches thick,
traversed by veins of silex, or opaline chalcedony, while the centre
is a silicified mass; in both states the internal structure may be
detected. This kind of fossil wood is to be seen in most cabinets, a
large quantity having been sent to England by emigrants.[144] These
fossil trees appear to have been subjected to the same mutations as
those of the Isle of Portland, for they are described as standing erect
to the height of several feet in a bed of arid sand, apparently in the
places where they grew; their petrified branches being scattered around
them. They so entirely preserve their natural appearance, that one of
the colonists mentions among the extraordinary sights he witnessed on
his first arrival in New Holland, the burning of trees into lime to
manure the ground.
[144] My late friend, Sir Francis Chantrey, had a magnificent specimen,
which, is now in the British Museum. See Petrifactions, p, 59.
[Sidenote: FOSSIL CONIFERÆ OF AUSTRALIA.]
A fossil pine forest, on the eastern coast of Australia, in the
inlet called Lake Macquarrie, is described by the Rev. B. Clarke, as
occurring at the base of a mountain range, composed of conglomerate and
sandstone, with subordinate beds of lignite; an alluvial plain extends
to the water's edge, covering the sandstone rock which is seen _in
situ_ beneath. Throughout this plain, stumps of fossil trees project
from the ground, and present the appearance of a forest in which the
trees have all been broken off at the same level. At the distance of
some yards from the shore, a reef is formed by vertical rows of the
petrified stems, which project out of the water. Many of the fossil
stems on the strand have the remains of roots extending into the
sandstone below the alluvial deposit, and, like those in the Island of
Portland, are in some instances surrounded by an accumulation of rock,
which forms a mound of a higher level than the surface of the stratum.
The trunks are, generally, three or four feet high, and from two to
six feet in diameter. The wood is silicified, and veins of chalcedony
traverse its substance between the concentric rings and medullary rays;
in several examples, from 60 to 120 annual circles of growth were
observable. Beds of lignite occur in the neighbouring hills, both above
and below the fossil trees; many localities along the eastern coast of
Australia are mentioned, as presenting similar phenomena. I may add
that the only fragment of petrified wood found by Mr. Walter Mantell in
New Zealand is coniferous.
In the valley of the Derwent, in Australia, opalized coniferous
trees of a similar character were observed under very extraordinary
circumstances, by the distinguished traveller, Count Strzelecki.
Truncated stems were found standing erect in a bed of scoriaceous
basalt (lava) and trachytic conglomerate: but in some instances only
basaltic casts of the trunks remain. This curious phenomenon can
only be explained by supposing the silicified stems to have resisted
the intense heat of the incandescent lava, while trees placed in
circumstances unfavourable to their petrifaction were consumed: but
the latter, being either saturated with water, or fresh and green,
were burnt slowly, and left cylindrical moulds in the cooled basaltic
scoriæ, with impressions of the external surface of the bark; these
moulds were filled Tip by a subsequent eruption, and thus basaltic
casts of the consumed trees were formed.[145]
[145] Physical Description of New South Wales, by Count Strzelecki.
Coniferous Wood in Oxford Clay.--It would occupy too much space to
notice the numerous localities in which fossil remains of conifers
occur in the Liassic and Oolitic formations of England.
In the Oxford and Kimmeridge Clays water-worn trunks and branches of
large pine-trees are often met with. An interesting deposit of these
remains was brought to light by my youngest son (Mr. Reginald Mantell),
when constructing the branch line of railway from the Great Western to
Trowbridge, in Wilts. In the progress of the work, extensive sections
were cut through the Oxford Clay, and laid bare a large quantity of
drifted wood, much of which was not petrified, but in the state of
bog-wood, and was used for fuel by the workmen. Trunks ten or twelve
feet long were met with, to which serpulæ, oysters (_Ostrea delta_),
and other shells were adherent. These vegetable remains were associated
with Belemnites, Belemnoteuthides, Ammonites, &c.; and had evidently
been drifted far out to sea by currents.[146]
[146] See _Wond._ p. 502. Geol. Journal, vol. vi. p. 311.
[Sidenote: FOSSIL CONIFEROUS WOOD.]
Coniferous Wood in the Chalk formation.--The arenaceous limestones
of the Greensand of Kent and Sussex abound, in some localities, in
water-worn masses of coniferous wood, which are often perforated by
boring mollusks, as _Teredo_, _Fistulana_, _Gastrochæna_, &c. In the
Iguanodon quarry of Kentish rag, near Maidstone, large quantities
of these remains occur, and Mr. Bensted has collected several cones
belonging to different kinds of conifers; one of these appears to be
a species of _Abies_, or Fir:[147] it was associated with fragments of
trunks and branches, whose internal structure proved their relation to
the fruit. _Plate V. fig. 2_, are microscopic views of transverse and
longitudinal sections of this wood; 2_a_ shows the cellular tissue in
a transverse slice, seen by reflected light; 2_b_ a vertical section
in the direction of the medullary rays, exhibiting the vessels studded
with single rows of glands. This wood occurs both in a calcareous and
siliceous state; in some examples the external zones are calcareous,
and the inner siliceous; in others the entire branch is changed into
black flint, in which the coniferous structure is beautifully preserved.
[147] It is figured and described as _Abies Benstedi_, by the Author.
Geol. Proc. January, 1843.
Near Willingdon, in Sussex (_Geol. S. E._ p. 172), a bed of sand,
immediately beneath the Galt, contains a layer of water-worn fragments
of stems and branches, of small size; they are generally perforated by
_Gastrochænce_, and the cavities formed by these depredators are filled
with particles of green chlorite sand. The structure of this wood is
represented in _Plate V. fig. 3^a_ a transverse, and 3_b_ a vertical
section, viewed by reflected light; in 3_b_ the vessels are dotted
with two parallel longitudinal rows of very minute glands, arranged
alternately, as in the Araucariæ; a fragment of one of the medullary
rays is seen near the middle of the specimen.
In this deposit of coniferous wood, two or more fruits apparently
referable to _Zamiæ_ have been discovered; one specimen, five and
a half inches long, and of an elongated cylindrical form, covered
with rhomboidal eminences, I have figured and described as _Zamites
Sussexiensis_.[148]
[148] Geol. Proc. 1843.
[Illustration: Lign. 58. Fragment of Coniferous Wood in Flint.
_From a wall in Lewes Priory,_]
The White Chalk of England has afforded but few traces of plants of
this family. Fragments of coniferous wood are, however, occasionally
found in the state of carbonaceous, or reddish brown friable masses,
and when this substance is removed, the surface of the chalk is seen to
be marked with impressions of ligneous fibres; sometimes the surface
is studded over with little pyriform eminences, which are cretaceous
casts of perforations made by insects in the wood. These specimens,
when all traces of the wood are absent, are very puzzling to those who
are not aware of their origin.
Occasionally silicified fragments of wood are found imbedded in flint.
I have an interesting specimen of this kind obtained from a wall in
Lewes Priory (_Lign. 58_), and though it must have been exposed to the
influence of the weather for nearly eight centuries, its surface still
exhibits coniferous structure.
[Sidenote: WOOD IN FLINT.]
Tertiary Coniferous Wood.--The Tertiary formations in some localities
abound in coniferous plants and trees, which, in the Paris basin,
are associated with bones of mammalia; several species of pine
(_Pinus_) and of yew (_Taxus_) from those deposits are described by M.
Brongniart. I have collected fossils of this kind from the London Clay
of the Isle of Sheppey, Bracklesham Bay, and Bognor in Sussex, and Alum
Bay, in the Isle of Wight; and from the plastic clay at Newhaven.
Fossil Foliage and Fruit of Conifers.--From this digression on the
pine-forests and drift-wood of the secondary formations, we return to
the examination of the foliage and fruits of this order of vegetables
that are preserved in the mineral kingdom.
Araucaria peregrina (_Lindley and Hutton_). _Lign. 59, fig.1._--With
the trunks and branches of conifers of the Lias, cones and foliage
are occasionally found: a beautiful example of a branch with the
leaves preserved, is figured, _Lign. 59_. This fossil has been so
admirably cleared from the shale which invested it (by Miss Philpot)
that even the surface of the leaves is exposed. It so closely
resembles a twig of _Altingia excelsa_, that the eminent authors of
Foss. Flor. have named it as above. But M. Brongniart states that the
foliage differs from that of the two living groups of Araucariæ: in
_Araucaria Brasiliensis_, the leaves are flat, in _Altingia excelsa_,
quadrangular; in the fossil the leaves are short, fleshy, arranged
spirally, and inserted.
[Illustration: Lign. 59.
Fig. 1.--Part of a Branch of Araucaria peregrina; _nat._
_Lias, Lyme Regis._
2.--Calamites nodosus with foliage; _nat._ _Coal-shale_,
(see _ante_, p. 109).
]
Pinites; a name applied to those fossil leaves and fruits which agree
in their general character with the recent genus Pinus; upwards
of thirty species are known.[149] In the Pines, as botanically
distinguished from the Firs (_Abies_), the leaves arise in bundles
of from two to five; and the scales of the cones are thickened, and
terminate in discs more or less defined. In Firs, (Larch, Cedar, &c.)
the scales have thin edges, and the leaves are solitary.
[149] See Endlechen's Synopsis Coniferarum.
Pinites Fittoni. _Geol. Isle of Wight_; 2d edit, p. 457.--Several cones
with the above characters have been found in the Wealden formation. A
cone figured and described by Dr Fitton, is remarkable for a double
prominence on each scale: It was supposed to resemble the fruit of
_Dammara_, but the strobilus of the latter is like that of the Cedar of
Lebanon, in which the edges of the scales are thin. The Wealden fossil
appears to be a genuine pine, and may be distinguished by the name of
its discoverer, _Pinites Fittoni_; a small figure of the only known
specimen is given, _Wond._ p. 399, _fig._ 4.
I have collected from the Wealden strata of the Isle of Wight three or
four small cones, which resemble those of a species of Araucaria; they
are ovate, imbricated, with acuminated scales, which are recurved at
the apex. The fossils figured in _Wond._ p. 399, _figs._ 2 and 3, are,
I believe, water-worn specimens of the same species.[150]
[150] I subjoin a definition of the genera Pinus and Abies, for the use
of the student.
Pinus.--_Fruit_-catkins ovate, roundish, or cylindrical closely set
with thick two-flowered scales; forming an imbricated cone, composed of
numerous ligneous angular, or flat, rigid scales, having attached to
the inside of each two seeds crowned with a thin membraneous, falcate,
oblong, or roundish wing; the scales are composed of a thick woody
substance, forming an angular surface, with a recurved point. The Pines
are evergreen trees, with from two to five narrow, angular leaves
springing from each sheath. Cotyledons four to twelve.
Abies.--Cones with thin flat scales, which are more membranous at the
extremities than in Pines: the leaves are emarginate, short solitary,
needle-shaped, angular or flat.
[Sidenote: WALCHIA.]
Walchia. _Lign. 60._--The fossil coniferæ thus named by Sternberg,
have numerous closely set, regularly pinnated branches, resembling
those of _Araucaria excelsa_, and which are thickly beset with foliage.
The leaves are sessile, compact, enlarged at the base, tetragonal
or falciform, and slightly decurrent; they often vary considerably
in form and length on the same bough. The branches are in some
examples terminated by oblong cones, composed of imbricated, oval or
lanceolate, pointed scales, the summits of which are not recurved,
as in the Araucariæ. The trees of this genus are closely related to
the _Araucaria excelsa_, and _A. Cunninghami_. Some species occur in
the Coal formation at St. Etienne and Autun;[151] others (as _Walchia
hypnoides_) in the schists of Lodève, and in the copper slates of the
Zechstein in Mansfeld.[152]
[151] "Mines de Houille de Vettin, &c." See "Tableau des Vég. Foss." p.
70, par M. Brongniart.
[152] Missing!
[Illustration: Lign. 60. Walchia hypnoides; 1/3 _nat._
_Permian, Lodève_.
Part of a bough with six of the branches bearing terminal cones.]
Abietites.--To the Abies, or Fir, several cones found in the Wealden
deposits of Sussex and Hants closely approximate in the form and
structure of their scales. The most remarkable is the very elongated
coniferous fruit, first discovered by me in the Wealden at Brook Point,
and described and figured in my Geology of the Isle of Wight (_2d
edit._ p. 452), under the name of _Abietites Dunkeri_, in honour of
the eminent geologist who has so successfully and diligently explored
the Wealden of the North of Germany.
I have been so fortunate as to collect from thirty to forty specimens
of these fruits of the conifers of the country of the Iguanodon,
associated with trunks and branches, and imperfect vestiges of single
lanceolate leaves.
[Illustration: Lign. 61.
Abietites Dunkeri.
_Wealden; Isle of Wight;_
1/3 _nat._
Fir-cone, showing the imbricated scales, and many bracteæ.]
[Sidenote: ABIETITES DUNKERI.]
Abietites Dunkeri. _Lign. 61._--These cones are of a cylindrical form,
and greatly elongated: the largest specimen is thirteen inches in
length, and but three inches in circumference. The scales are broad,
slightly convex without and concave within, obovate or subrotund, with
a prominent midrib, edges thin and entire. Leaves solitary, slender,
slightly curved, from 1 inch to 1-1/2 inch in length. The cones
were garnished with bracteæ, which are seen on the margins of the
fossil when imbedded in the rock. Whether the foliage that forms the
constituent substance of a large proportion of the bituminous coal of
Hanover (_ante_, p. 74), and which has been figured and of the named
by Dr. Dunker _Abietites Linkii_, belongs to the same species of Fir
as these cones, I am unable to determine. The seeds are of an ovate
form: the pericarp is in the state of carbon, and filled or lined with
pyrites or calc-spar.
These cones are generally found more or less pyritified, and are
extremely beautiful objects when first collected; but like the fruits
from the Isle of Sheppey, similarly mineralized, often decompose, in
spite of every precaution, after exposure to the air but for a few
weeks.
A small sub-ovate fir-cone found with coniferous wood in the
Kentish-rag of Mr. Bensted's quarry, near Maidstone, (_ante_, p. 173),
and figured and described by me as _Abies Benstedi_, probably belongs
to the coniferæ of the Wealden, since it was associated with drifted
bones of the Iguanodon.
Fossil Cypresses.--The tribe of conifers called _Cupressus_ or Cypress,
(distinguished from the firs and pines by the leaves being mere scales,
and the cones consisting of small wooded peltate bracteæ, and by other
botanical characters,) including the Juniper and Arbor-vitæ, appears to
have flourished during the whole of the secondary epochs; for fossil
leaves and stems referable to this family, but whose generic affinities
cannot be determined with precision, have been found in the Trias,
Lias, Oolite, and Wealden deposits.
[Illustration: Lign. 62.
Thuites Kurrianus _nat._
_Wealden. Hastings._]
Thuites Kurrianus. _Lign. 62._--The _Thuja_ or Arbor-vitæ, a plant too
well known to require description, is the type of the fossil plants
distinguished by the name of _Thuites_. Many years since I discovered
vestiges of branches and leaves of some species of this genus, in the
ironstone of the Wealden beds, at Heathfield in Sussex (_Geol. S. E._
p. 228); and of late, many specimens have been found in strata of
the same formation in England and Germany. The branch here figured,
from the cabinet of S. H. Beckles, Esq. will serve to illustrate
the appearance of these fossil plants. Some small fruits found in
the ironstone of Heathfield may possibly belong to Cypresses. The
foliage and fruit of five or six distinct species of Thuites have been
discovered in Tertiary strata.
Voltzia.[153] (_Wond._ p. 547).--This extinct genus of plants is
peculiar to the Trias (_Grès bigarré_) or New Red deposits, and is
one of the most characteristic of the fossil coniferæ. The specimens
first found were from _Sultz-les-Bains_, near Strasburgh. The leaves
are alternate, arranged spirally, sessile, and decurrent, and have
much analogy with those of certain Araucariæ. The fruits are oblong
cones, with cuneiform scales, slightly imbricated, not contiguous, and
generally with from three to five lobes.
[153] Named in honour of the late M. Voltz, of Strasburgh, by whom they
were first discovered. The specimens in the British Museum, from my
collection, were presented to me by M. Voltz.
[Sidenote: TAXITES. NŒGGERATHIA. FOSSIL RESINS.]
Taxites.--Some branches found in the Stonesfield slate, and bearing a
general resemblance to twigs of Yew (_Taxus_), are described under the
above name, but their analogies are doubtful. (See _ante_, p. 145.)
Nœggerathia.[154]--I must briefly notice the coal-plants which M.
Brongniart has placed under this genus, because the foliage of some
species appears to have entered largely into the formation of certain
seams of coal, although the perfect form of the leaves is unknown.
The foliage referred to Nœggerathia consist of pinnated, or deeply
pinnatifid, simple leaves. These leaves, or leaflets, are either
elongated, linear, lanceolate, wedge-shaped or flabelliform, and
entire, or deeply lobed at their extremity, and are traversed by
numerous, fine, equal nerves, slightly diverging from the base, but
almost parallel. The affinities of these plants are not satisfactorily
made out: M. Brongniart considers them to approach nearest to the
Cycads or Conifers; perhaps forming a connecting tribe between those
two great groups of gymnosperms.[155]
[154] A leaf of _N. flabellata_ is figured in Foss. Flor.
[155] Tab. Veg. Foss. p. 64.
Fossil Resins.--Amber.--The resinous secretions of Conifers are
occasionally found in a fossil state. When the tunnel was carried
through Highgate Hill, in 1811, concretionary lumps of a brittle
substance were discovered, which proved, upon analysis, to be the
resin of a coniferous tree changed by mineralization. In a bed of
fossil wood, near Hythe, in Kent, a resin was found that partook
of the properties of amber and retinasphalt; it was of a clear red
colour, very infusible, and acted upon with difficulty by many chemical
solvents.[156]
[156] Geological Proceedings, 1843.
The pollen of pines or firs occurs in a tertiary deposit at Egra, in
Bohemia; this bed is entirely composed of pollen and the frustules of
many kinds of diatomaceæ.[157]
[157] Described by M. Ehrenberg.
[Sidenote: AMBER. FOSSIL PALMS.]
_Amber_, so remarkable for its electrical properties, and so largely
used for ornamental purposes, is a fossil resin, the product of an
extinct species of pine (_Pinus succinifer_), which, though nearly
allied to _Pinus abies_, and _P. picea_, is essentially distinct.
The Amber in the European markets is principally collected from the
shores of the Baltic, between Memel and Konigsberg, being washed out of
submerged beds of lignite, and thrown up on the strand by the waves.
Amber is occasionally found on the eastern and northern shores of
England. The forests of Amber-pines appear to have been situated in
the south-eastern part of what is now the bed of the Baltic, in about
55° north latitude, and 37° to 38° east longitude, and were probably
destroyed at the commencement of the Drift period.
Insects, spiders, small crustaceans, leaves, and fragments of vegetable
tissue, are often imbedded in amber; and a few hairs and feathers of
mammalia and birds have been detected. These organic bodies must have
become immersed in this substance when it exuded from the trees in a
viscid state, for they are often preserved as fresh and beautiful as
if recently embalmed in the liquid resin. Upwards of 800 species of
insects have been discovered, chiefly referable to Aptera, Diptera,
Neuroptera, Coleoptera, Libellula, &c.: by far the greater number
belong to extinct forms.
The vegetable remains comprise four species of pine, and species of
cedar, cypress, juniper, yew; and of oak, poplar, beech, ash, &c.; and
a few ferns, mosses, liverworts, confervæ, and fungi. The Amber appears
to have exuded from the bark and wood, but chiefly from the root-stock,
as is the case with the _Copal_ and _Animé_, which are resinous
substances obtained from certain trees in India and America, and
largely employed for varnish: these resins are often substituted for
true amber, especially when they contain insects, &c.; but the latter
are always of the existing indigenous species of the country. The
difference observable in the colour of the various species of amber, is
attributable to accidental chemical admixtures.[158]
[158] Petrifactions, p. 23.
Fossil Palms (_Palmacites_).--Reserving an account of the fossil
plants belonging to the other grand division of Dicotyledons, the
_Angiosperms_ (_ante_, p. 61), for the last section of the present
chapter, I proceed to notice the most important family of the
_Endogens_, or _Monocotyledons_, whose remains occur abundantly in many
tertiary deposits--the Palms.
The Palms are, for the most part, lofty trees, having a single
cylindrical stem, which, like that of the arborescent ferns, rises to
a great height, and is crowned with a canopy of foliage. The trunks
are solid, most dense on the outer part, and in some species (as the
Cane-palms) are coated with a thin siliceous epidermis. At a little
distance above the surface of the ground, strong, simple, rope-like
roots are sent off from the stem, appearing like clusters of stays or
braces to support the trunk; and the base of the petrified palm-trees
often exhibits vestiges of these organs.[159] The leaves are supported
by petioles, and are in most species very large;[160] they are either
pinnated or flabellated (fan-shaped), and sometimes nearly split
in half: the veins or nervures are parallel, and the interspaces
plaited like the folds of a fan. The surface of the stem is scored
by transverse scars formed by the separation of the petioles, and
these markings assist in the identification of the fossil trunks
of palm-trees. The fruit is in some kinds a single drupe, as the
Cocoa-nut; in others a cluster of soft pericarps, as the Date.
[159] Specimens in the Brit. Mus. Petrifactions, p. 12.
[160] In the Fan-palm (_Corypha_), the leaf is sometimes twenty feet
broad.
The Palm family is divided into upwards of sixty genera, comprising
more than a thousand species: the greater number are inhabitants of
tropical countries. Stems, with the external surface and internal
structure preserved, and the foliage, and fruit, of several kinds of
Palms, have been found in a fossil state, and chiefly in the Tertiary
formations. Examples of the large silicified palm-stems from the
West India Islands, where they occur imbedded with corals petrified
in the same manner, are to be seen in the British Museum,[161] and
most public collections: and sliced polished sections, exhibiting
the monocotyledonous structure, are common in private cabinets. The
endogenous organization of the stems is so obvious as to leave no doubt
as to the class to which the trees belong, but M. Brongniart states,
that, in the absence of the foliage and fruit, it is seldom possible to
pronounce with certainty that a fossil monocotyledonous stem belongs to
a Palm; for the internal structure alone does not enable the botanist
to fix upon any characters which will distinguish the stems of Palms
from those of Pandanus, Agave, Yucca, Aloes, Dracæna, &c. Fossil
monocotyledons known by their stems only, are therefore arranged by M.
Brongniart under the general name of _Endogenites_.
[161] Petrifactions, p. 52.
The _Palmacites carbonigenus_ of Corda, and other supposed palm-trees
of the Coal formation, are regarded by the same eminent botanist as
essentially differing in structure from this family, and belonging to
an extinct tribe of exogens.
That a large proportion of the exogenous stems found in the Tertiary
deposits are true palms, there can, however, be no doubt, for the
foliage and fruit, which are occasionally associated with them, confirm
the inference drawn from the characters of the trunks.
[Sidenote: FOSSIL PALM LEAVES.]
Stems, leaves, and fruits of Palms have been discovered in the Paris
basin, by M. Ad. Brongniart (_Bd._ pl. lxiv. p. 515); and silicified
trunks in many other places on the Continent; but no fossils of this
kind surpass in beauty and interest those which are found in the West
Indies. A slice of a silicified stem from Antigua is represented, as
seen by reflected light, in _Plate V. fig. 1_; it admirably displays
bundles of vessels imbedded in cellular tissue.
Silicified stems of monocotyledons, related to the Palms, are very
widely distributed, and have been collected among mammalian remains in
Ava, and in the Sub-Himalaya mountains.
Fossil Palm-leaves.--The pinnated and fan-shaped leaves of the Palms
are so peculiar as to be easily recognized in a fossil state. Though
many specimens have been found in the tertiary strata of the Continent,
but two or three examples have been met with in England. The first
discovered British specimen is in my cabinet, and was obtained by
Mr. Fowlstone, of Ryde, from the fresh-water limestone of Whitecliff
Bay, in the Isle of Wight. It is thirteen inches in length, and
eleven in width: fresh-water shells and plants are imbedded with it.
It is figured in Geol. I. of Wight, _2d edit._ p. 431. This species
(_Palmacites Lamanonis_) occurs also at Aix in Provence, in great
perfection, associated with Insects, Fishes, fresh-water shells, &c.
(_Wond._ p. 260. _Petrif._ p. 62).
Twelve species of palm-leaves are enumerated by M. Unger, from the
Tertiary deposits of the Continent. One species has been found in
the Chalk formation of Silesia; the most ancient strata in which the
remains of undoubted palms have as yet been observed.
The fossil palm-leaves of the pinnated form are named _Phœnicites_,[FF]
and examples occur in the Tertiary grits of Puy en Velais, I am not
aware that leaves of this type have been found in England: diligent
research in our tertiary leaf-beds (at Whitecliff Bay, Alum Bay,
Bournemouth, Wareham) will probably sooner or later discover them. The
leaflets have a well-marked median nerve, with fine nervures running
parallel with it; a character by which the foliage of _Phœnicites_ may
be distinguished from that of the Cycadeæ.
[162] From _Phœnix dactylifera_: the Date-Palm.
Fossil Fruits of Palms.--Although certain fruits found in the
coal-measures have been referred to the palm-tribe by M. Unger, Dr.
Lindley, and other botanists, M. Brongniart is of opinion that no such
identification can be established; the same remark applies to the
Carpolithes from the Oolite; in fine, the Tertiary deposits have alone
yielded fruits that can be unquestionably referred to plants of this
order. The most productive British locality of fossil fruits of Palms,
and of many other vegetables, is the Island of Sheppey; and I purpose
describing in this place, not only the remains of this family, but also
of the other plants associated with them.
[Sidenote: FOSSIL FRUITS OF THE ISLE OF SHEPPEY.]
Fossil Fruits of the Isle of Sheppey.--This little island, which is
situated in the mouth of the Thames, is entirely composed of the
London Clay, with bands of septaria. On the north, there is a range
of cliffs, about two hundred feet high, which is being continually
undermined by the waves, and large masses of the clay are thrown down,
and innumerable fruits, seeds, branches and stems of trees, and other
fossils, are exposed on the strand at low-water. The vegetables are
strongly impregnated with iron pyrites, and as this mineral speedily
decomposes when exposed to the atmosphere, the choicest examples often
fall to pieces, even when preserved in the cabinet.[163] The nodular
masses of indurated clay, termed septaria, contain the best preserved
and most durable fossils. The fossil fruits, or carpolithes, occur
in such profusion, that a large collection can easily be made; they
comprise several hundred species, few of which have been scientifically
investigated.[164]
[163] Mr. Bowerbank, who possesses an unrivalled collection of these
fruits, keeps them in stopper-bottles filled with water, placing
the different species separately, and labelling the phials. I have
successfully employed mastic varnish, first wiping the specimens dry,
and removing any saline efflorescence by means of raw cotton, and then
brushing in the varnish with a stiff hair-pencil.
[164] See vol. ii. Excursion to the Isle of Sheppey.
Mr. Parkinson has given admirable figures of several of the Sheppey
fruits, particularly of the large palm-like nuts, called "_petrified
figs_" (_Org. Rem._ vol. i. pl. vi. vii. _Pict. Atlas_, pl. vi. vii.)
M. Ad. Brongniart has named several in his _Prodrome_; but without
figures the descriptions are useless to the student. Mr. Bowerbank
has published two numbers of a work entitled, "_History of the Fossil
Fruits of the London Clay_," with seventeen plates; from which I have
selected a few subjects for illustration. The fruits described are the
following:
1. Fruits having a downy structure, like the Cotton plant.
2. _Cucumites._ Seeds of plants of the cucumber family. _Lign._
63, _fig._ 1 and 3. These fossil fruits so closely resemble
the seeds of various members of the recent genus _Cucumis_,
or Cucumber, comprising the Gourd, Water-melon, &c., both in
outward form and internal structure, that there is no reasonable
doubt of their belonging to plants of the same family; hence the
name _Cucumites_ or fossil cucumbers.
3. Cones of a tree allied to the genus _Petrophila_, of New
Holland. _Lign._ 63, _figs._ 2 and 8.
4. Seeds of the Bean family, some of which resemble those of the
common Scarlet-runner. _Lign._ 63. _figs._ 5, 6, 7.
5. _Wetherellia_; pulpy fruits divided into two lobes by the
expansion of the ripe seeds. As the section thus exposed bears
some resemblance to a coffee-berry, these fossils are popularly
called petrified coffee-berries. This genus has no known living
representative. _Lign. 63, fig. 4_.
6. Fruits allied to the Palm tribe. (_Nipadites_). _Lign._ 63,
_fig._ 9, and 10.
7. Fruits of leguminous plants, differing from any known recent.
_Lign._ 64, _figs._ 1, 2, 3, 4.
8. Seeds, allied to the _Amomum_, or Cardamom tribe. _Lign. 64,
fig. 5_.
9. Seeds of _Cupressinites_, or plants related to the Cypress.
10. Seeds resembling those of the _Laburnum_.
11. Seed-pod of a species of _Acacia_, or _Mimosa_. _Lign. 64,
fig. 7._--2/3 _nat._
[Illustration: Lign. 63. Fossil Fruits from the Isle of Sheppey.
_London Clay._
Fig. 1 and 3.--_Cucumites variabilis_: fig. 3, is a vertical section,
showing the seeds. _Lign._ 64, fig. 6--1/2 _nat._
2 and 8.--_Petrophiloides Richardsoni_: 1/3 _nat._ Fig. 8, is a
vertical section, showing the disposition of the seeds in the
cells formed by the confluent scales--1/2 _nat._
4.--_Wetherellia variabilis_: a section of the fruit, in which state
it is called coffee-berry by the collectors--1/3 _nat._
5 and 6.--_Faboidea semicurvilinearis_: fig. 5, side view--
1/4 _nat._
6.--Is the face of a similar seed--1/3 _nat._
7.--_Faboidea bifalcis_: side view--1/3 _nat._
9.--_Nipadites lanceolatus_: _a_, the seed; _b_, the shell, or
pericarp--1/2 _nat._
10.--_Nipadites cordiformis_: _a_, the extremity of the seed,
imbedded in the shell--1/3 _nat._
]
[Illustration: Lign. 64. Fossil Fruits from the Isle of Sheppey.
_London Clay._
Fig. 1 and 2.--_Zulinosprionites latus_. 2. A section, showing the
receptacles for two seeds.--2/3 _nat._
3.--_Leguminosites dimidiatus_; side view.--1/2 _nat._
4.--_Leguminosites subquadrangularis_; side view.--1/2 _nat._
5.--_Cupanoides lobatus._--1/2 _nat._
6.--_Cucumites variabilis._--1/2 _nat._
7.--_Mimosites Browniana_; from Ossington, Suffolk. A seed-pod of an
_Acacia_, or other plant of the _Mimosa_ family.--2/3 _nat._
]
Nipadites. _Lign. 63_. (_Pict. Atlas_, pl. vi. vii.)--The most
remarkable fruits in the above catalogue are those which, from their
appearance when compressed, are known to collectors by the name of
"_petrified figs_" (_Lign. 63, fig. 9, 10_). Some specimens attain
a considerable size, and are from five to seven inches long. The nut,
and the pericarp or shell, are often well preserved. These fossils were
referred to the _Cocos_ by Mr. Parkinson, but they have not a ligneous
endocarp with three pores as in the Cocoa-nut.
Mr. Bowerbank has shown that they are nearly related to the fruit of
the Nipa, or Molucca-Palm, a tree which abounds in Bengal, and in the
Molucca and Philippine Islands. The Nipæ are low, shrub-like plants,
having the general aspect of palms; they grow in marshy tracts, at the
mouths of great rivers, particularly where the waters are brackish.
They are allied to the Cocoa-nut tribe, on the one hand, and to the
_Pandanus_, or Screw-pine, on the other.
The _Nipadites_, according to Mr. Bowerbank, have the epicarp and
endocarp thin and membranous, and the sarcocarp thick and pulpy, and
composed of cellular tissue, through which run numerous bundles of
vessels. Nearly in the centre of the pericarp is situated a large
seed which, when broken, is more or less hollow. This seed consists
of regular layers of cells, radiating from a spot situated near the
middle, and apparently inclosing a central embryo.
The same author remarks, that "if the habits of the plants to which
the fossil fruits belonged were similar to those of the recent _Nipa_,
it will account for their abundance in the London Clay in the Isle of
Sheppey; which formation, from the great variety of stems and branches,
mixed up with star-fishes, shells of mollusks, and bones of fishes,
crustaceans, and reptiles of numerous marine and fresh-water genera,
is strikingly characteristic of the delta of a river, which probably
flowed from near the Equator towards the spot where these interesting
relics are deposited." The fact that the seed-vessels of several
species of Nipadites abound in the Isle of Sheppey, and have not been
observed in any other locality in England, tends to support this
opinion.
Carpolithes of this kind occur in great perfection in the Eocene
strata of Belgium, and were figured and described, nearly seventy
years since, in Burton's "_Oryctographie de Bruxelles_," as petrified
cocoa-nuts; the uncompressed state in which these fossils occur makes
the resemblance to the recent fruit more striking than in the flattened
pyritous specimens from the clay of Sheppey.
[Sidenote: NIPADITES OF BELGIUM.]
The _Nipadites_ of Brussels have recently been brought under the more
immediate notice of English geologists, in a memoir "On the Tertiary
Strata of Belgium and French Flanders," by Sir Charles Lyell, in
which several specimens are figured and described.[165] These fossils
are found in sands and sandstone, presumed to be of the age of the
Bracklesham beds of Sussex. They are procured from Schaerbeek, in the
northern suburbs of Brussels, where extensive quarries are worked for
paving-stones, and have long been celebrated for remains of turtles,
trunks of palms, and dicotyledonous trees, and the fruits, now called
Nipadites. The vegetable remains often occur silicified; Sir C. Lyell
was shown by the workmen "the trunk of a petrified exogenous tree, with
forty rings of annual growth; it had lain in a horizontal position, and
was bored by teredinæ. The silicified base of the trunk of a Palm-tree,
apparently broken off short at about the level of the soil, had
numerous air-roots, or rootlets, attached."[166]
[165] Quarterly Journal of the Geological Society of London, vol. viii.
August 1852.
[166] "On the Belgian Tertiary Formations," Geol. Journal, vol. viii, p.
344.
Of the thirteen species of Nipadites enumerated by Mr. Bowerbank,
some of which are, however, only accidental varieties, four have been
identified among those obtained from Schaerbeek: two of them belong
to but one species--the _Nipadites Burtoni_: the others are _N.
lanceolata_ (_Lign. 63, fig. 9_), and _N. Parkinsoni_ (_Pictorial
Atlas_, plate vii.). These fossil nuts closely resemble the fruit of
_Nipas fruticans_, a palm which abounds in the delta of the Ganges,
and other parts of Bengal, and is the only living species of the
genus known.[167] In an immature or abortive specimen of _Nipadites
giganteus_ (of Bowerbank), figured in _Geol. Journ._ pl. xix. fig. 2,
the angularity of the pericarp observable in the ripe fruit (_Lign.
63. fig. 9_) is well marked. The largest specimen of Nipadites from
Schaerbeek, is above seven inches long and four wide. The arenaceous
strata containing these fruits, and stems of palms and dicotyledonous
trees, are supposed to have been formed in the sea near the mouth of
a river, as in the case of the clay-beds at Sheppey: the vegetable
remains are associated with bones of fresh-water Turtles, teeth of
Sharks, cases and spines of Echinoderms, and shells of the genera
Ostrea, Pinna, &c.[168]
[167] "On the Belgian Tertiary Formations," Geol. Journal, vol. viii. p.
344.
[168] Geol. Journal, vol. viii. p. 347.
* * * * *
[Sidenote: FOSSIL PANDANUS.]
Fossil Fruit of Pandanus. (_Popocarya._ _Bd._ pl. lxii. p. 503.)--The
_Pandanaceæ_ are monocotyledonous trees, named Screw Pines from the
spiral insertion of their long, rigid, sword-like leaves, along the
stem; they are natives of hot climates, and abound in the groups of
islands in the Pacific; being generally the first important vegetable
tenants of the newly-formed Atols or coral-islands. As in the palms,
the stem is supported near the base by long side-roots, which enable
these trees to maintain an erect position, and flourish on the
newly-elevated coral-reefs, where but little soil has accumulated.
The existence of this tribe of plants during the secondary ages is
known only by a single example of a fossil fruit, which was discovered
by Mr. Page, of Bishport, in the Inferior Oolite, to the east of
Charmouth, Dorsetshire, and is preserved in the museum at Oxford; no
vestiges of the stems or foliage have been observed.
[Illustration: Lign. 65. Fossil Wood with Teredines; _nat._
_London Clay, Regent's Park._
Fig. 1.--A polished transverse section, showing the tubes lined with
spar.
2.--Portions of mineralized Teredines, seen in relief on the wood.
]
This carpolithe, (for a detailed account and figures see _Bd._ p. 504,
pl. lxiii.) is of the size of a large orange; the surface is covered
with a stellated epicarpium, composed of hexagonal tubercles forming
the summits of cells which occupy the entire circumference of the
fruit. Each cell contains a single seed, usually hexagonal, resembling
a small grain of rice, and is supported by a foot-stalk, formed of
dense fibres; a character exhibited only by the seed-vessels of
Pandanus. The fossil fruit differs from that of the recent Screw-pines
in the seeds being neither inclosed in a hard nut, nor collected into
drupes, but dispersed uniformly over the entire mass; this forms the
essential generic distinction between them. Dr. Buckland has named this
unique carpolithe _Podocarya_. (_Bd._ p. 505.)
Wood perforated by Teredinæ. _Lign. 65._--The drifted trunks and masses
of wood found in the London Clay, at Sheppey, Bognor, Bracklesham, &c.,
some of which belong to Palms, others to Conifers, and Dicotyledons,
are commonly more or less perforated by the boring mollusks called
_Teredo_, or _Teredina_; and remains of their testaceous tubes are
often well preserved. The tortuous channels excavated in the wood by
these borers, are lined or filled up with calcareous spar, indurated
clay, or other mineral matter, of various shades of grey, blue, yellow,
&c.; and the polished slabs of this fossil wood are beautifully
diversified by the sections of the sparry tubes, crossed at right
angles by the ligneous structure; as in the specimen _fig. 1, Lign.
65_, from the Canal in the Regent's Park.[169]
[169] Slabs of this kind are generally kept by the lapidaries at Bognor,
Worthing, &c. and sold at 2_s._ or 2_s._ 6_d._ each.
In the fossil, _fig. 2. Lign. 65_, from the Isle of Sheppey, the
tubes of the teredinæ are seen in relief, in consequence of the surface
of the block of wood having decayed and been removed.
Fossil Liliaceæ.--The family of endogens, termed _Liliaceæ_, comprises
many beautiful plants; those with annual stems, as the Lily, Hyacinth,
Tulip, &c. are well known for the variety and splendour of their
blossoms; some of the arborescent forms, as the Tulip-tree, attain a
large size, but the flowers of this division are relatively small.
In tertiary strata, the stems, leaves, fruits, and even the imprints
of flowers, have been discovered, of plants related to _Sagittaria_
(Arrow-head), _Smilax_ (Bind-weed), _Convallaria_ (Lily of the valley),
&c.
The Dracæna (_Dragon-blood tree_), a tall, slender, elegant tree with
amplexicaul leaves (common in our hot-houses), belongs to this family;
and certain stems found with Clathrariæ, and bones of the Iguanodon,
in the Kentish-rag at Maidstone (_ante_, p. 173), so closely resemble
the trunk of this plant, that they have been named by Mr. König,[170]
_Dracæna Benstedi_; the specimens are in the British Museum. Until the
internal structure of these fossils has been examined, the correctness
of this identification is, however, uncertain: the external
resemblance to the stem of the Dracæna consists in the interrupted
annular ridges, denoting amplexicaul leaves: no vestiges of the foliage
have been observed.
[170] Petrifactions, p. 49.
[Sidenote: FRESH-WATER PLANTS. FOSSIL CHARÆ.]
Fossil Fresh-water Plants.--The tertiary fresh-water strata often
contain abundance of the remains of the aquatic vegetables that
inhabited the lakes and rivers in which those deposits were formed. The
remains of several species of the common lacustrine plant, the _Chara_,
are found in immense quantities in the fresh-water limestones and marls
of the Isle of Wight, of the coast of Hampshire, and of the Paris
Basin. The shell-marls, still in progress of formation in the lakes of
Scotland, and the travertine precipitated from thermal springs, in like
manner envelop and preserve the leaves and fruits of recent species.
Fossil Fruits of Chara. (_Gyrogonites._) _Lign. 66._--The Chara is a
well-known inhabitant of almost every stream and rivulet. The stems
are hollow, and composed of tubes filled with a fluid in which green
globules circulate; they form beautiful microscopic objects for
exhibiting the circulation in vegetables. The fruit consists of very
small nuclei, contained in a calcareous pericarp, composed of five
spirally twisted plates, that unite at the summit. These seed-vessels,
when first discovered in a fossil state, were supposed to be the shells
of mollusks, and a genus was formed for their reception with the name
of _Gyrogonites_ (_twisted-stones_); a term still employed, though the
vegetable nature of these bodies is well known. In _Plate III. fig. 5_,
a branch of the common Chara with seeds is represented: and figures
of the seed-vessels, of two fossil species are given in _Lign. 66,
figs. 1, 2_.
Specimens of the fossil fruits and stems of Charæ, may be collected
in abundance in the fresh-water limestone at East Cliff Bay, Isle of
Wight.[171]
[171] See my Geology of the Isle of Wight, _Lign. 5_, p. 109.
[Illustration: Lign. 66. Fossil Fresh-water Plants.
_Eocene, Paris._
Fig. 1.--Seed-vessel of _Chara helicteres_ × 10; side view.
1_a_.--View of the base of the same.
1_b_.--One of the spiral valves separated.
1_c_.--View from above.
2.--Seed-vessel of _Chara medicaginula_ × 10. The upper
figure is a side view: the lower, a view of the base.
3.--_Carpolithes ovulum_, magnified side view.
3_a_.--The same, natural size.
3_b_.--Magnified view of the base of the same.
4.--A piece of fresh-water limestone, with impressions
of two stems of _Nymphea arethusa_ ×.
]
The _Purbeck beds_ at Durlstone Bay, near Swanage, also contain
numerous Gyrogonites associated with fresh-water shells. The bands of
siliceous sinter, which occur in the lowermost deposits, are especially
rich in these remains.[172]
[172] I am indebted to the Rev. Osmond Fisher, of Dorchester, for a fine
suite of these and other interesting fossils from the Purbeck beds of
Ridgway and Osmington, near Weymouth; and to William Shipp, Esq., of
Blandford, and Edward Woodhouse, Esq., of Ansty, for many specimens
from Durlstone Bay, and Ridgway.
_Fossil Nympheæ._ _Lign. 66, fig. 4._--Those magnificent aquatic
plants, the Water-Lilies (_Nympheæ_), that adorn our rivers and lakes
with flowers and foliage which partake more of the characters of
an exotic flora than any other of our indigenous plants, are also
found fossil in the lacustrine marls and limestones of the tertiary
formations of France; but the nature of these remains could only be
recognized by a profound botanist, for they consist of impressions of
the internal structure of the stems, which, however, is so peculiar,
that no reasonable doubt of their origin can be entertained. Two
imprints on a piece of limestone from Lonjumeau, presented to me by the
late M. Alex. Brongniart, are figured in _Lign. 66, fig. 4_; some
minute seed-vessels (_Lign. 66, fig. 3_), found with them, closely
resemble those of _Nympheæ_, and are supposed to belong to the same
plants (_Class. Vég. Foss._ p. 72).
Fossil Flowers.--The tertiary limestones of Monte Bolca (_Wond._ p.
565), so rich in ichthyolites, and other fossil remains of great
interest, contain leaves, and even flowers, of liliaceous plants.
The specimen figured (_Lign. 67, fig. 3_) is in the Museum at
Paris, and described by M. Brongniart under the name of _Antholithes_
(stone-flower) _liliaceus_; it consists of the corolla and calyx:
the anthers and pistils have not been observed in any example. The
discovery of this fossil should excite the young collector to search
diligently for such objects in the tertiary strata of England.
[Sidenote: FOSSIL ANGIOSPERMS.]
Fossil Angiosperms.--The fossil remains of the class which constitutes
the grand features of the existing floras of most countries, the
_Exogenous Angiosperms_, are now to be considered; and though our
survey of fossil botany has partaken but little of a geological
arrangement, yet the reader may have observed, that a large proportion
of the vegetables composing the floras of the ancient secondary
formations, belonged to the Cryptogamous and Gymnospermous classes.
A striking contrast is presented in the geological position of the
mineralized dicotyledonous plants, of existing genera. These abound in
the tertiary strata, and generally in an inverse ratio to the antiquity
of the deposit, while their remains are almost wholly absent in the
older rocks; neither have there been discovered in the Tertiary,
any beds of vascular cryptogamia, at all approaching the immense
accumulations in the Carboniferous formations.
[Illustration: Lign. 67. Fossil Nuts, and Flower.
Fig. 1.--Thalictroides Parisensis; Tertiary strata, Paris.
2.--Thalictroides Websteri. Isle of Wight.
3.--Antholithes liliaceus. Monte Bolca.
4.--Juglans nux-taurinensis: fossil Walnut, Turin.
4_a_.---Portion of the husk of the shell.
4_b_.--The kernel, formed of calcareous spar.
]
The most remarkable exception, is the single instance of a large leaf
of a dicotyledonous plant in the Trias, or New Red sandstone, near
Liverpool, described by Sir Roderick Murchison, which much resembles
the foliage of a thick-ribbed Cabbage.[FQ]
[173] This fossil is named _Dictyophyllum crassinervium_, by Dr. Lindley,
Foss. Flor. pl. cci. and is figured, Sil. Syst. p. 43.
It would be impossible, within the limits necessarily assigned to
these volumes, to offer even a general view of the fossil remains of
this grand class of vegetables; our remarks must be limited to a few
interesting examples and localities.
When stems of dicotyledonous trees only are found, but little certainty
can be obtained as to the family to which they belonged; the foliage of
many well-known genera offer more positive characters; the flowers are
rarely in a state of preservation to afford any valuable data; but the
fruits, or seed-vessels, are frequently well preserved, and these may
enable the botanist to arrive at precise determinations as to generic,
and, perhaps, specific relations.
The tertiary marls of Aix, in Provence, which abound in insects,
crustaceans, and lacustrine shells, contain many kinds of
dicotyledonous leaves, associated with those of palms. (_Wond._ p. 260.)
The Lignite, or Brown-coal deposits, are almost entirely composed of
dicotyledonous trees, belonging to many genera, which are inhabitants
of Europe; namely, the Poplar, Willow, Elm, Chestnut, Walnut, Sycamore,
Maple, Linden, Buckthorn, Vine, &c. (_Bd._ vol. i. pp. 508-514.)
The beds of brown coal, on the banks of the Rhine, are literally
carbonized submerged forests, which in some remote period were drifted
from the interior of the Continent into a vast lake or gulf; for the
trees bear evident marks of transport, and are destitute of roots and
branches. These masses resemble the rafts of forest trees, which are
daily floated down the Mississippi into the Atlantic, where they become
engulfed in the profound depths of the ocean, and probably will be
converted into coal or lignite; and in future ages, may be elevated
above the waters, become dry land, and present to the then existing
communities of mankind an inexhaustible supply of mineral fuel,
composed of species and genera of plants, which possibly may then be
extinct, and replaced by peculiar types of vegetation.
Fossil Flora of Œningen. (_Bd._ pp. 511-514).--The celebrated
lacustrine tertiary formation of Œningen, whose fossil reptiles and
mammalia we shall have to notice hereafter, contains a rich assemblage
of dicotyledonous and gymnospermous ligneous vegetables, with a few
ferns and grasses. Not only branches and leaves of a species of
Vine[174] occur, but even the fruit; fossil grapes being found in these
deposits;[175] there are also many aquatic plants. A descriptive list
of these fossils, by Professor Braun, of Carlsruhe, is given by Dr.
Buckland. The brown-coal of this basin is in thin beds of but little
economical importance, but so rich in the vegetation of the miocene
tertiary period, that a few days spent in collecting those treasures
will amply reward the intelligent tourist who may visit Constance. (See
_Wond._ p. 263.)
[174] See Knorr, Mon. des Catastrophes, pl. xxxviii. tom. i.
[175] Fossil grapes from the lignite of Œningen were exhibited by Dr.
Daubeny at a late meeting of the Geological Society.
[Sidenote: FOSSIL DICOTYLEDONOUS LEAVES.]
The foliage of dicotyledonous trees frequently occurs in the Eocene
marls and limestones, and in some localities in considerable abundance,
and in beautiful preservation. Near Bournemouth, on the Hampshire
coast, the leaves of many species are met with in a bed of sandy
marl, between three and four feet thick: the vegetable substance
is carbonized; some of the leaves are referable to the _Lauraceæ_
and _Amentaceæ_, others to the _Characeæ_;[176] a similar deposit of
tertiary plants has been discovered near Wareham. These beds belong to
the lower group of the Hampshire Basin.[177]
[176] Geol. Proc. vol. iii. p. 592.
[177] As the seed-vessels and other vegetable remains in the Isle
of Sheppey are all of a tropical character, while those found in
the Eocene strata of Alum Bay, Bournemouth, and Newhaven, are of a
temperate climate, as Nerium, Platanus, &c., Prof. E. Forbes infers
that the former were transported from distant lands by currents, and
that the latter belong to the true flora of the country inhabited by
the Palæotheria and other associated mammalia.
[Illustration: Lign. 68. Imprints of Dicotyledonous Leaves in Gypseous
Marl.
_Tertiary. Stradella, near Pavia._
Fig. 1.--Leaf of Poplar (_Populus græca_).
2.--------- Maple (_Acer_).
3.--------- Water-spike (_Potamogeton_).
4.--------- Willow (_Salix_).
5.--------- Chestnut (_Æsculvs_).
]
The red marlstone associated with lignite in the plastic clay beds
at Castle Hill, Newhaven (_Geol. S. E._ p. 54), contains leaves of a
similar kind; a seed-vessel of a coniferous tree has also been found in
it.
Some of the most interesting examples of dicotyledonous leaves
that have come under my notice, are from the Sub-Apennine tertiary
strata, at Stradella, near Pavia. They belong to several genera of
arborescent, or at least ligneous plants, and most of them to species
which still grow in Italy. In some examples the substance of the
leaves is changed into carbon, and the structure well preserved; but,
in general, sharp imprints on the stone are the only traces of the
originals. They are found in a gypseous marl, of a cream colour; and,
from their perfect state, it is inferred that they were enveloped in
the soft matrix immediately after their fall, and preserved by the
rapid crystallization of the gypsum. Two specimens from my cabinet are
figured in _Plate III._ _figs._ 4 and 8; and outlines of a few other
examples, in _Lign. 68_.
Carpolithes (_Fossil Fruits_).--In the description of the fossil
fruits from the Isle of Sheppey, several kinds of dicotyledons were
included. Many species also abound in the lignites of Germany, France,
and Italy; in those near Frankfort, seed-vessels of the Maple, Elm,
Hornbeam, Birch, Willow, and Walnut, &c. In the environs of Turin,
fruits of a species of Walnut (_Juglans_, _Lign. 67_), occur in the
newer tertiary deposits, and are called Turin-nuts; the ligneous
envelope has perished, but the form of its surface, and of the inclosed
kernel, is preserved in calcareous spar. These nuts differ, both in
the pericarp and kernel, from the living species: the lobes are simple
(_Lign. 67, fig. 4^b_), and not subdivided as in the common walnut;
a species has been discovered at Lons-le-Saulnier, in which the lobes
are mamillated.
Two kinds of fruits belonging to plants of the order _Ranunculaceæ_,
and related to _Thalictrum_ (_Meadow-rue_), have been found in the
eocene deposits of France and England; one in the Paris basin,
(_meulière du terrain d'eau douce supérieur_,) by M. Alexandre
Brongniart, and the other in the Isle of Wight, by Mr. Webster. In the
specimen from the last-named locality the pericarp is carbonized, and
its cavity filled with clay. Figures of these seed-vessels are given in
_Lign. 67, figs. 1, 2_.
Carpolithes Smithiæ.--I would notice in this place some very
remarkable fossil fruits that are occasionally met with in the White
Chalk of Sussex and Kent, and appear to belong to dicotyledonous trees.
The first specimen was discovered by me in a chalk-pit near Lewes, and
is described in my "Fossils of the South Downs:" some illustrative
examples collected by Mrs Smith, of Tunbridge Wells, tending to
elucidate the nature of the original more satisfactorily than those
in my collection, are figured and described by me in the Journal of
the Geological Society, 1843, under the above name. These fruits are
of an oval form, about one and a half inch long, and one inch wide,
and are pressed almost flat. They are of a rich burnt-sienna colour,
mottled with white, from the chalk having permeated their substance,
and are studded over with slight eminences, which are the exposed
summits of oblong flattened seeds. Although the internal structure is
not preserved, there can be no doubt that the originals were spurious
compound berries, having, like the Mulberry, the seeds imbedded in a
soft pulpy mass.
[Sidenote: FOSSIL DICOTYLEDONOUS TREES.]
Fossil Dicotyledonous Trees.--The occurrence of trunks and branches of
angiospermous trees in a carbonized state has already been described;
like the monocotyledons and conifers, they also occur silicified.
The most beautiful specimens I have seen are from the Lybian and
Egyptian deserts, and were collected by my friend, the late Colonel
Head. In these the most delicate vascular tissue is permeated by
chalcedony and jasper, and the vessels are filled with silex of a
bright vermilion and blue colour, while the cellular structure is of a
rich yellow. Fragments of these fossil trees are scattered everywhere
among the sands of the desert; the most interesting locality is an
irregular plateau, which reposes on marine limestone, considerably
above the level of the Nile, about seven miles east by south from
Cairo. This district is called the _petrified forest_, from the immense
quantities of silicified trees with which it is covered. It is thus
graphically described by a late traveller:--
"Having passed the tombs of the Caliphs, just beyond the gates of
Cairo, we proceed to the southward nearly at right angles to the road,
across the Desert to Suez: and after travelling some ten miles up a
low barren valley covered with sand, gravel, and sea-shells, fresh
as if the tide had retired but yesterday, we cross a low range of
sand-hills, which has for some distance run parallel to our path. The
scene now presented is beyond conception singular and desolate. Heaps
of fragments of large trees converted into stone everywhere meet the
eye, and when struck by our horses' hoofs rang like cast iron; they
extend for miles in the form of a decayed and prostrate forest; and the
appearance is so natural, that were it in Scotland or Ireland, it would
pass without remark as a drained bog, on which the exhumed trees lay
rotting in the sun. The roots, and rudiments of the branches, are in
many cases nearly perfect, and in some the worm-holes eaten under the
bark are distinctly recognizable."[178]
[178] Bombay Times.
Many of the trunks are scattered over the surface, among rolled and
angular fragments of dark grit, and pebbles of jasper,[179] chert,
and quartz. The large trunks occur in great numbers on dark-coloured
knolls, where they lie, like the broken stems of a prostrate forest,
crossing each other at various angles. Two of the largest measured
respectively forty-eight, and sixty feet in length, and two and
a half, and three feet in diameter, at the base. With but two or
three exceptions, all the specimens examined microscopically, are
dicotyledons. No traces of seed-vessels or leaves have been detected.
[179] The jaspers are known to lapidaries as _Egyptian Pebbles_.
The situation and condition of these petrified forests, indicate great
changes in the relative position of the land and sea in that part of
Egypt; for the trees must have grown on the dry land formed by the
elevated bottom of a former ocean; which must have subsided, and been
covered by beds of sand and pebbles; another elevatory movement must
have raised the entire series of deposits to their present situation,
and the retiring waters have removed the loose portions of the last
formed strata, and dispersed them, with fragments of the silicified
trees, over the surface of the Egyptian and Lybian deserts.[180]
[180] See a Memoir on the Geology of Egypt, Geol. Proc. vol. iii. p.
782; and on the Petrified Forest near Cairo, vol. iv. p. 349, by Lieut.
Newbold, F.R.S.
[Sidenote: DICOTYLEDONOUS OF THE CRETACEOUS EPOCH.]
Dicotyledons of the Cretaceous Epoch.--Among the crowd of interesting
facts relating to the botanical character of the earlier periods of
geology which recent observations have brought to light, one discovery
demands especial notice, and I have reserved it for this place, rather
than introduce it in an earlier section.
In the neighbourhood of Aix-la-Chapelle the lower members of the
Cretaceous formation, viz. the Greensand, Galt, and Chalk-marl, are
well developed, and comprise a series of littoral deposits of the
great Chalk ocean that extended westwardly between France and England,
on both sides of the existing Channel, and eastwardly over North and
Central Germany, Sweden, Poland, and Russia, far into Asia. The series
of strata at Aix-la-Chapelle is several hundred feet in thickness, and
the lowermost beds lie immediately on the Carboniferous rocks of the
country.
Dr. M. H. Debey,[181] to whose scientific labours we are indebted for an
accurate knowledge of these interesting facts, divides these cretaceous
deposits into four groups, the lowermost of which appears to be the
equivalent of our Greensand; it consists of beds of clay and sand, the
middle portion abounding in stems, leaves, and fruit, and the resin of
coniferous trees.
[181] See Geol. Journal, vol. vii. p. 109.
The epidermis of the leaves often occurs in a carbonized state, and is
recognizable by its microscopic structure. Xylophagous mollusks are
found in the petrified and carbonized wood. Fresh-water Desmidiaceæ,
and a few marine remains, are associated with this fossil flora, which
is distinguished by the abundance of Ferns and dicotyledonous leaves,
and the scarcity of Cycads; among them are undoubted _Proteaceæ_.
The specimens collected by M. Debey from the lower cretaceous beds are
the following:
Algæ, 15. Filices, 28. Hydropteridæ, 2. Cycadeæ, 5. Naiadeæ, 5. Palmæ,
1. Coniferæ, 20. Julifloræ, 5. Credneriæ, 3. Leaves of Dicotyledons,
undetermined, 26. Fruits undetermined, 8. Woods.[182]
[182] Geol. Journal, vol. vii. p. 111.
This assemblage of angiosperms, with gymnosperms, and cryptogamia, at
the commencement of the Cretaceous epoch, when the Iguanodon and other
reptilian forms of the Oolite and Wealden still inhabited the land
and water, proves, as Sir Charles Lyell has remarked,[183] that the
meteorological phenomena of that remote period differed in no essential
particular from those which now prevail.
[183] Supplement to the New Edition of Elements of Geology, 1852, p. XV.
* * * * *
RETROSPECT OF FOSSIL BOTANY.
[Sidenote: RETROSPECT OF FOSSIL BOTANY.]
If we pass from the consideration of details of structure, and of
botanical affinities, to a general survey of the mineralized remains of
the vegetable kingdom, we perceive that from the palæozoic deposits,
to those which are contemporaneous with the human race,--from the
coal-measures to the peat-bogs of modern times,--vast accumulations
of vegetable matter, in various states of carbonization, have
been produced from the imbedded relics of the terrestrial floras
that flourished during the respective periods of their formation;
petrifaction, or the transmutation of vegetable tissues into stone,
from the infiltration of siliceous, calcareous, or metallic solutions,
being an accidental process, dependent on the physical conditions under
which the trees and plants were submerged, and entombed in the strata.
Although the entire system of vegetable life which prevailed during
the earlier ages of the world is but partially revealed by the fossil
remains which geological researches have brought under the examination
of the naturalist,--for numerous tribes of plants may have existed
of which no traces have been detected, while of species of delicate
tissues all vestiges may have perished,--yet a review of the facts
hitherto obtained, presents some highly important and unexpected
results, as to the characters of the successive floras which prevailed
during the palæozoic, secondary, and tertiary epochs. And though
deductions of this nature must, in the present state of our knowledge,
be regarded in the light of shifting hypotheses to be modified or
abandoned with the progress of discovery,--yet the predominating types
which characterize the flora of one system of formations, differ so
essentially from those of another, that it may be reasonably inferred
such apparent distinctions are the effect of organic laws, and not
illusions arising from our misinterpretation of the natural records of
former conditions of the vegetable world.
The absence in the most ancient deposits of the entire class of
Angiosperms, or flowering plants, which constitutes the leading
features of the floras with which we are familiar,--the abundance of
unknown types of Cryptogamia, and the extinction or disappearance of
those tribes in the succeeding formations, and the prevalence of new
species and genera belonging to another class;--the predominance in
one flora, both in number and variety, of certain tribes, and their
decadence in the next period; while a family subordinate in the
antecedent epoch, and known but by a small number of species, suddenly
acquires a pre-eminence both in numbers and variety;--are phenomena,
which the facts brought before us in the course of this argument,
present in a striking point of view.
Assuming these data as the basis of a philosophical generalization,
M. Brongniart arranges the known species of fossil plants into three
grand systems, which correspond with the great geological periods,
comprehended in the palæozoic, secondary, and tertiary formations.
The first or most ancient flora is characterized by the predominance of
_Cryptogamic Acrogens_--the _Ferns_ and _Club-mosses_; the second by
the large development of the _Dicotyledonous Gymnosperms_--the _Cycads_
and _Conifers_: the third by the appearance and prevalence of the
_Angiosperms_, both dicotyledonous and monocotyledonous. The following
table presents a concise view of the results of M. Brongniart's
investigation.[184]
[184] For details, and a masterly review of the subject, the original
Memoir must be consulted. See Tableau des Genres de Végétaux Fossiles,
considérés sur le point de vue de leur Classification Botanique et de
leur Distribution Géologique, par M. Adolphe Brongniart. Paris, 1849.
CHARACTER OF THE FLORAS. GEOLOGICAL EPOCHS.
I. Règne des Acrogènes; the Flora } The _Devonian_, _Carboniferous_,
of Vascular Cryptogamia. } and _Permian_, Formations.
II. Règne des Gymnospermes; the } The _Triassic_, _Jurassic_ (or
Flora of Cycadaceæ and Coniferæ. } _Lias_ and _Oolite_), and
} _Wealden_, Formations.
III. Règne des Angiospermes. } The _Cretaceous_, and _Tertiary_
Flora of Dicotyledonous and } (_Eocene_, _Miocene_, and
Monocotyledonous flowering } _Pliocene_), Formations.
plants, or Angiosperms. }
It must be observed that this table is only designed to indicate the
successive _predominance_ of each of the three classes of the vegetable
kingdom, in the respective epochs, and not the entire exclusion of the
others. Thus, in the two first, both Acrogens and Gymnosperms existed;
but in the first period the former greatly exceeded the latter, both
in number and magnitude; while in the next the Gymnosperms acquired the
ascendancy; but in both these epochs, from the Devonian to the Wealden
inclusive, very few if any Angiosperms, or flowering dicotyledons,
existed. With the Cretaceous period the Angiosperms appear in great
numbers, and in the Tertiary epochs acquire the importance they possess
in the existing floras.
The following analysis of the flora of the Carboniferous epoch, by M.
Brongniart, will exemplify these remarks.[185]
[185] See Wonders of Geology, vol. ii. pp. 726-733, for an account of
the Carboniferous floras and deposits.
ANALYSIS OF THE CARBONIFEROUS FLORA
Cryptogamia (_Amphigens_). Algæ 4
Champignons 6
--- 6
(_Acrogens_). Ferns 250
Lycopodiaceæ (Club-mosses) 83
Equisetaceæ 13
--- 346
Dicotyledonous Gymnosperms. Asterophyllites 44
Sigillariæ 60
Nœggerathiæ 12
Cycadeæ? 3
Coniferæ 16
--- 135
_Dicotyledonous Angiosperms_ 0
_Monocotyledons?_ (very doubtful) 15
---
502
---
Thus out of five hundred species, 352 are Cryptogamia; and with the
exception of six, belong to the Acrogens.[186]
[186] Bronn gives the annexed numerical summary of the fossil and recent
species of plants:--
_Plants._--Cellular 188 Fossil. 9,100 Living.
Vascular 1,867 60,303
----- ------
2,055 69,403 (80,000, Lindley.)
----- ------
In conclusion, I must direct attention to a remarkable character of the
palæozoic and secondary floras, namely, the almost entire absence of
the _Gramineæ_ or Grasses, which constitute so large a proportion of
the existing vegetation.
Above six hundred species of plants have been discovered in the British
strata;[187] and yet two species of _Poa_ (a tribe of grasses), from
Coalbrook Dale, are the only known examples of Gramineæ. It has been
suggested that the greater or lesser durability of the foliage of
certain vegetables, may have occasioned their presence or absence in
the carboniferous deposits, and experiments were instituted by Dr.
Lindley with the view of determining this question. But though it was
found that, when the foliage of various families was subjected to
long maceration, the leaves of dicotyledons and grasses disappeared,
while those of ferns and cycads remained, this fact does not meet the
exigencies of the case, for we have no evidence to show that the fossil
leaves were ever placed in similar conditions; on the contrary, there
is reason to conclude that they were imbedded under circumstances that
arrested the usual progress of decomposition, prevented the escape
of the hydrogen and other gaseous elements, and gave rise to the
bituminous fermentation by which they were converted into lignite and
coal; and we have no proof that, had grasses been associated with the
ferns, they would not have undergone a similar change. Moreover, there
are countries in which the ferns now assume the numerical proportion of
the grasses of other latitudes; for example. New Zealand, which also
presents in its fauna a striking analogy to that of the carboniferous
deposits, in the almost entire absence of indigenous mammalia; one
species of Rat being the only known living quadruped.
[187] See Mr. Morris's Catalogue of British Fossils.
On this subject Dr. Dieffenbach remarks, that "although in its flora
New Zealand has some relationship with the two large continents between
which it is situated, America and Australia, and even possesses some
species identical with those of Europe, without the Latter being
referable to an introduction by Europeans, yet the greater number of
species, and even genera, are peculiar to it. New Zealand, with the
adjacent islands, Chatham, Auckland, and Macquarrie, forms a botanical
centre. It is sufficiently distant from both continents to preserve
its botanical peculiarities, and it offers the most striking instance
of an acknowledged fact in all branches of natural history, viz. that
the different regions of the globe are endowed with peculiar forms of
animal and vegetable life. The number of species of plants at present
known is 632, of which 314 are dicotyledonous, and the rest, or 318,
are monocotyledonous and cellular. The monocotyledons are few in
comparison with the cellular plants, for there are but seventy-six
species. The grasses have given way to ferns, for the ferns and
fern-like plants are by far the most abundant in New Zealand, and cover
immense districts. They _replace the Gramineæ_ of other countries, and
give a character to all the open land of the hills and plains. Some
of the arborescent kinds grow to thirty feet and more in height, and
the variety and elegance of their forms, from the minutest species to
the most gigantic, are very remarkable."[188] In the accumulations of
vegetable matter now in the progress of formation in the morasses,
bays, and creeks of New Zealand, the remains of ferns largely
predominate; and I am informed by my son,[189] that in the estuaries
they are associated with numerous shells of brachiopodous mollusca.
[188] Dr. Dieffenbach's New Zealand.
[189] Mr. Walter Mantell, of Wellington, New Zealand.
* * * * *
ON COLLECTING BRITISH FOSSIL VEGETABLES.
[Sidenote: ON COLLECTING FOSSIL VEGETABLES.]
From what has been advanced, the student will perceive that to obtain
an illustrative collection of the fossil plants of Great Britain, many
different localities must be visited.
The fruits and stems of Palms, Conifers, and many dicotyledons, may be
collected in the Isle of Sheppey, and other places where the London
Clay is exposed. (See _Excursion to the Isle of Sheppey_, Part IV.)
Cycadeous stems and coniferous wood may be procured in the Isle of
Portland; from the Wealden Cliffs along the southern shore of the Isle
of Wight; and on the Sussex coast, from Bexhill, by St. Leonard's,
to the east of Hastings. The foliage of several species of Zamiæ and
ferns, occur abundantly in the lower Oolite, along the Yorkshire coast,
near Scarborough, and at Gristhorpe Bay. The Lias of Lyme Regis,
Charmouth, and their vicinity, affords stems and branches of coniferous
trees, and leaves of cycads.
Ferns, Sigillariæ, Calamites, and the usual plants of the carboniferous
flora, may be found in every coal-mine; and the Devonian limestones
of the South of Ireland yield ferns and Lepidodendra. In Forfarshire
the lower Devonian shales abound in the foliage of aquatic, apparently
fluviatile, plants.[190]
[190] See Memoir on the Telerpeton; Geol. Journ. vol. viii. p. 106.
A list of some of the most productive British localities is subjoined.
In addition to the suggestions already given as to the mode of
collecting specimens, it may be necessary to state that the leaves in
the tertiary marls and clays are generally very delicate and friable,
and liable to flake off in the state of a carbonaceous film. This may,
in a great measure, be prevented by carefully covering them with a thin
coating either of mastic varnish, or gum-water, before they are placed
in the cabinet. In extracting these specimens, a broad chisel will
be found the most convenient instrument. In searching for fossils in
coal-mines, the collector should remember that the ironstone nodules
often contain beautiful examples of the leaves of ferns, and fruits of
Lepidodendra. These nodules, when of an oblong shape, should be split
open in a longitudinal direction, by a smart blow of a hammer, and the
inclosed leaf will thus be exposed, as shown in _Lign. 3, figs. 2, 3_,
_ante_, p. 69.
* * * * *
BRITISH LOCALITIES OF FOSSIL VEGETABLES.
[Sidenote: BRITISH LOCALITIES OF FOSSIL VEGETABLES.]
Allenbank, Berwickshire _Carb._ Stems of Conifers, &c.
Alum Bay, Isle of Wight _Tert._ { Fruit, dicotyledonous leaves,
{ lignite; Charge, stems and
{ seed-vessels.
Ashby-de-la-Zouch, } _Carb._ { Coal plants in great abundance.
Leicestershire }
Bignor, Sussex } _Cret._ } Fucoids.
} _Firestone_ }
Binstead Quarries, near } _Tert._ { Charæ, stems and seed-vessels.
Ryde, Isle of Wight }
Blackdown, Devonshire _Gr. Sand._ Silicified wood--coniferous.
Bognor, Sussex _Tert._ { Coniferous and monocotyledonous
{ wood; washed
{ up on the shore.
Bolton, Lancashire _Carb._ Lepidodendra, Sigillariæ, &c.
Bournemouth, Hants _Tert._ { Dicotyledonous leaves.[191]
[191] Fruits and Fern-leaves have been collected here by Mr. Beckles and
stems of a species of _Arundo_, by Mr. Alfred Woodhouse.
Brook-point, Isle of Wight _Wealden_ { Cycads, and coniferous
{ wood.
Burdie House, near Edinburgh _Carb._ Ferns, wood, &c.
Calbourn, Isle of Wight _Tert._ Charæ, stems and fruits.
Camerton, near Bath _Carb._ Usual plants of the coal.
Charmouth, Dorset _Oolite_ { Coniferous wood; Cycads;
{ fruit of Pandanus.
Clifton, near Manchester _Carb._ { Coal plants in great
{ perfection.
Coalbrook Dale, Shropshire _Carb._ { Usual plants of the coal, in
{ abundance. The ironstone
{ nodules are rich in
{ fern-leaves, fruits of
{ lepidodendrons, &c.
Cuckfield, Sussex _Wealden_ { Clathraria, Endogenites,
{ Ferns, and Lignite.
Durlstone Bay, near Swanage _Wealden_ { Charæ; Gyrogonites in
{ abundance.
Folkstone, Kent _Galt_ { Coniferous wood--bituminous,
{ and pyritified.
Glasgow _Carb._ { Coal plants, and large trunks
{ of Coniferæ.
Hastings, Sussex _Wealden_ { Clathrariæ, Cycads,
{ Endogenites, Ferns, Thuites,
{ &c.
Herne Bay, Kent { _London { Fruits of Conifers, and
{ Clay_ { Palms: wood.
Kilkenny, Ireland _Carb._ Calamites, ferns, &c.
Knocktopher, nr. Kilkenny, } _Devonian_ } Ferns, Lepidodendrons, &c.
Ireland } }
Leeds _Carb._ { Beautiful coal-plants from
{ the pits in the vicinity.
Liverpool _New Red_ Fuci.
Lyme Regis, Dorset _Lias_ Cycads; Conifers; wood.
Maidstone, Kent _Greensand_ { Fruits and wood of Abies,
{ Pinus, Dracæna; Fuci.
Malton _Oolite_ Fruits, and Cycads.
Newcastle (Jarrow Colliery) _Carb._ { Coal plants in great
{ variety.[192]
[192] In collecting _Stigmariæ_, the student should particularly attend
to the relation existing between these fossils and their supposed
stems; for it is probable that roots of this type will be found to
belong to other genera, besides Sigillaria, and Lepidodendron (_ante_,
p. 136).
Newhaven (Castle Hill), } _Tert._ { Dicotyledonous leaves and
Sussex { fruit--_rarely_.
Portishead (on the shore) } _Millstone } Sigillariæ, Stigmariæ, &c.
} Grit_ }
Portland, Isle of _Wealden_ { Petrified forest of Conifers,
{ with Cycads.
Pounceford, Sussex _Wealden_ Equiseta, Ferns, Lignite.
Runswick, Yorkshire Coast { _Lower } Cycads, Ferns, &c.
{ Oolite_ }
Saltwick, near Whitby { _Lower } Foliage of Cycads, Ferns, &c.
{ Oolite_ }
Sandown Bay, Isle of Wight _Wealden_ Conifers, Cycads, wood.
Scarborough _Oolite_ Ferns, Cycads, Equiseta, &c.
Selmeston, Sussex { _Greensand_ } Coniferous wood.
Sheppey, Isle of { _London { Fruits innumerable, wood,
{ Clay_ { &c. (_ante_, p. 186.)
Stonesfield, Oxfordshire _Oolite_ Fuci, Cycads, Thuites, &c.
Swindon, Wilts _Oolite_ Coniferous wood, & Cycads.
Tunbridge Wells (vicinity) _Wealden_ Ferns, several species.
Ventnor, Isle of Wight _Firestone_ Clathraria, Conifers.
Wareham, Dorset _Tert._ { Dicotyledonous foliage, and
{ Palm-leaves.
Whitecliff Bay, I. of Wight _Tert._ Palm-leaves, Charæ, &c.
Whitwick, Leicestershire _Carb._ The usual coal-plants.
The above list must, of course, be considered as merely suggestive:
many other localities are mentioned in the previous notices of the
fossil genera.
PART III.
⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼
FOSSIL ZOOLOGY.
"The very ground on which we tread, and the mountains that surround
us, are vast tumuli in which the Organic Remains of a Former World are
enshrined."--Parkinson.
The existing species of animals scientifically determined by
naturalists amount to upwards of one hundred thousand, while those
known in a fossil state scarcely exceed twenty-five thousand; yet the
latter comprise examples of all the classes, and most of the families
and genera, which still inhabit our planet. Although our notice of
these remains must necessarily be very general, we shall endeavour to
describe all that are of peculiar interest, either in a geological
or zoological point of view; or which from their prevalence, or wide
distribution, will frequently be met with by the collector in the
course of his researches.
Our examination will commence with animal organisms of the simplest
structure, and proceed in an ascending order, in accordance with the
usual zoological classifications; but, as in the botanical department,
it will be convenient occasionally to include the consideration of
the fossil remains of more than one family in the same section, when
associated in a particular locality or deposit.
In the preliminary remarks on the nature of Organic Remains (_ante_, p.
43), the various conditions in which the durable structures of animals
are preserved in the mineral kingdom, were fully explained; we may
therefore at once enter upon the investigation of this most important
division of our subject; that to which the term _Palæontology_, is,
indeed, restricted by some authors.
The fossil remains of the animal kingdom will be treated of under the
following heads:--
I. Zoophytes: including--
1. Porifera, or Amorphozoa: the most simple animal
structures; as the _Sponges_.
2. Polypifera, or Polypiaria; _Coral-animals_.
3. Bryozoa, or _Molluscan Zoophytes_; as the _Flustræ_.
II. Echinodermata, or Echinoderms; Comprising--
1. Crinoidea; or Lily-shaped animals.
2. Asteriadæ; _Star-fishes_.
3. Echinidæ; _Sea-urchins_.
III. Mollusca, or Mollusks. Under this head not only
the fossil shells of testaceous mollusca, but also
those of a lower order of animals, the _Rhizopodes_,
or _Foraminifera_, will be treated of.
1. Foraminifera.
2. Bivalves: the Lamellibranchia, and Brachiopoda.
3. Univalves: the Gasteropoda and Pteropoda.
4. Cephalopoda; those with chambered shells, as the _Nautilus_
and _Ammonite_; and the naked tribes, the Sepiadæ,
or _Cuttle-fish_.
IV. Articulata. (Animals protected by a hard jointed
envelope or case.)
1. Cirripedia: as the _Balanus_, or Barnacle.
2. Annelida: red-blooded worms, as the _Serpulidæ_.
3. Insecta, and Arachnida or _Spiders_.
4. Crustacea; including _Crabs_, _Lobsters_, _Trilobites_, &c.
V. Pisces; or Fishes.
VI. Reptilia; or Reptiles.
VII. Aves; or Birds.
VIII. Mammalia.
IX. Man.