the Floras of each of these epochs of formation, do not prevent each
of them having characters of its own, and often an assemblage of
species, almost all peculiar to each particular epoch. We ought,
therefore, to distinguish here those various subdivisions, the number
of which will perhaps be afterwards multiplied, when we become better
acquainted with the vegetables of each of the stages of the Jurassic
formations.
"_Keupric Epoch._--M. Brongniart then gives an enumeration of the
vegetables of the Keupric epoch, which, in regard to the Amphigenous
cryptogams, consist of Algæ; in regard to the Acrogenous cryptogams,
of Ferns and Equisetaceæ; in the case of the Gymnospermous
dicotyledons of Cycadeæ and Coniferæ; lastly, of two doubtful
monocotyledons (_Palæoxyris_ and _Preisleria_.)
"On comparing this Flora with that of the variegated sandstone of the
Vosges, and with that of the Lias, we perceive that it has nothing in
common with the first except the palæoxyris, which appears very nearly
related to that of the variegated sandstone; on the contrary, it
resembles the Flora of the Lias or Oolite in the ferns, many of which
are specifically identical, or nearly allied in the _Nilsonia_ and
_Pterophyllum_, which are likewise either identical, or very nearly
connected specifically with the Lias.
"_Lias Epoch._--The Liasic epoch furnishes Amphigenous cryptogams,
consisting of Algæ, mushrooms, and lichens; Acrogenous cryptogams,
such as Ferns, Marsileaceæ, Lycopodiaceæ, and Equisetaceæ;
Gymnospermous dicotyledons, represented by the Cycadeæ and Coniferæ;
finally, doubtful monocotyledons, consisting of _Proacites_ and
_Cyperites_.
"The essential characters of this epoch are therefore, _1st_, The
great predominance of Cycadeæ, already well established, and the
presence of numerous genera in this family, particularly _Zamites_ and
_Nilsonia_; _2d_, The existence of many genera among the ferns with
reticulated nerves, which scarcely shew themselves, and under forms
not greatly varied, in the most ancient formations; but some of which,
notwithstanding, already begin to appear in the epoch of the Keuper.
Such are the _Camptopteris_ and _Thaumatopteris_.
"_Oolitic Epoch._--The Oolitic epoch furnishes, among Amphigenous
cryptogams, the Algæ; among the Acrogenous cryptogams, Ferns,
Marsileaceæ, Lycopodiaceæ, and Equisetaceæ; among the Gymnospermous
dicotyledons, Cycadeæ and Coniferæ; lastly, among the doubtful
monocotyledons, Podocarya and Carpolithes.
"This list is chiefly founded on the fossils, so varied in character,
collected on the coasts of Yorkshire, near Whitby and Scarborough, in
beds which are referred to different parts of the inferior oolite, and
particularly to the great oolite. It likewise contains a small number
of species found in the slaty limestone of Stonesfield, near Oxford,
depending on these same beds.
"In France, the fossils of this formation have been collected in the
neighbourhood of Morestel, near Lyon, by Dr Lortet; at Orbagnoux and
Abergemens, near Nantua, in the department of the Ain, by M. Itier; in
the vicinity of Chateauroux, near Châtillon-sur-Seine, by Colonel
Moret; at Mamers, in the department of Sarthe, by M. Desnoyers; and,
lastly, in the greatest quantity by M. Moreau, in beds of oolithic
limestone of a very pure white, in the neighbourhood of Verdun, and
near Vaucouleurs. Some species have likewise been found at other
points of the Jura, in Normandy, near Valogne, in the neighbourhood of
Alençon, in each of these localities in very small number. But the
greater part of these species are not yet described and figured, and
they generally differ as species from those of England. The ferns are
generally less numerous, and not so well preserved; we must, however,
except the _Hymenophyllites macrophyllus_, found in a perfect state at
Morestel, and likewise observed at Stonesfield, and in Germany. The
Cycadeæ, the species of which are not greatly varied, are referrible
to the genera _Otozamites_ and _Zamites_; Ctenis, Pterophyllum, and
Nilsonia have not yet been observed; lastly, the Coniferæ of the genus
_Brachyphyllum_ are there particularly abundant, and more frequent
than in the other localities.
"In Germany, it is more especially in the slaty limestone of
Solenhofen, near Aichstædt, that these fossils have been observed, and
particularly those of the family of Algæ. M. Gæppert likewise notices
many Cycadeæ in the Jurassic formation of Ludwigsdorf, near Kreuzburg,
in Silesia.
"But these localities, so diverse, are referrible to very different
stages of the Oolithic series, and perhaps will constitute, when they
are better known, and more fully explored, distinct epochs.
"The distinctive characters of this epoch, comprising the whole extent
we have assigned to it, from the Lias to the Wealdean formation
exclusively, are; among the Ferns, the rarity of ferns with
reticulated nervures, so numerous in the Lias; among the Cycadeæ, the
frequency of _Otozamites_ and _Zamites_, properly so called; that is
to say, Cycadeæ most analogous to those of the existing period, and
the diminution of _Ctenis_, _Pterophyllum_, and _Nilsonia_, genera
much more remote from living species; finally, the greater frequency
of Coniferæ, viz., _Brachyphyllum_ and _Thuites_, much rarer in the
Lias.
"_Wealdean Epoch._--This epoch affords, Amphigenous cryptogams, the
Algæ; among Acrogenous cryptogams, Ferns, _Marsileaceæ_, and
_Equisetaceæ_; among Gymnospermous dicotyledons, _Cycadeæ_ and
_Coniferæ_; lastly, some Carpolithes as plants of a doubtful class.
"This enumeration results principally from discoveries made, in recent
years, in the Wealdean formations of the north of Germany, at
Osterwald, Schaumberg, Buckeburg, Oberkirke, &c., of which the fossil
plants were first described by M. Ræmer, and afterwards in a more
complete manner by M. Dunker, in his monograph of these formations. To
these species must be added others, less numerous and varied,
previously discovered in the _Wealds_ of England, near Tilgate Forest,
and Hastings in Sussex, and which are so well described by M.
Mantell."
This same formation has likewise been found in France, near Beauvais,
by M. Graves, who observed there _Lonchopteris Mantelli_, and some
other plants, of which M. Brongniart has not seen specimens, and which
he quotes from Graves on the geology of the department of the Oise.
"These species, 61 in number, enumerated above, appear to be all
peculiar to this formation, with the exception, perhaps, of _Baiera
Huttoni_, which seems to be identical with the species of the Bayreuth
Lias and Scarborough Lias; but their generic forms are almost all the
same as those of the Lias and Oolitic formations. The Cycadeæ,
however, already appear less numerous relatively to the ferns.
"We further observe, that this fresh-water formation, which, according
to our view, terminates the reign of the Gymnosperms is connected, by
the whole of its characters with other epochs of the vegetation of the
Jurassic formation, and is distinguished from the Cretaceous epoch,
which succeeds it, by the complete absence of every species which
could be arranged among the Angiospermous dicotyledons, both in France
and England, as well as in the deposits of northern Germany, so rich
in varied species. On the contrary, in the lower chalk, cretaceous
_glauconia_, the quadersandstein or planerkalk of Germany, we
immediately find many kinds of leaves evidently belonging to the great
division of Angiospermous dicotyledons, as well as some remains of
palms, of which no trace is observable in the Wealdean deposits.
"I class among the Cycadeæ the stems of the Tilgate forest, formerly
designated by the name of _Clatharia Lyellii_, and which I have
considered as a stem related to the _Dracæna_. The whole of its
characters, although the almost entire absence of the tissues prevents
us examining its anatomy, appear to me to render this connection most
probable, and particularly to indicate the relations between this stem
and that of _Zamites gigas_ found at Scarborough.
"The abundance of Lonchopteris Mantelli is a character of the Wealdean
formations of the south of England and the department of the Oise,
where this fossil seems to make its appearance, at least in fragments,
in the greater number of localities, where these beds are exposed by
the excavation of potter's clay in this formation, near Savignies. In
Germany, on the contrary, this species is wanting, and _Abietites
Linkii_ becomes the predominating plant. With regard to Brachyphyllum,
I have not yet had it in my power to study them in a natural state;
but the figures given of them leave little doubt as to their analogy
with the species of the Oolitic epoch.
"The abundance of the Cycadeæ likewise forms a distinctive character
of the Wealdean formations of Germany. Still there are, as has been
seen, many species common to the two basins; and I may add, that
probably the Sphenopteris Goepperti, _Dunk._, does not differ from
Sphenopteris Phillipsii, _Mant._
"I have not included in this list some marine plants mentioned as
belonging to the beds of this epoch; _1st_, because it appears to me
doubtful whether they really belong to the Wealdean and not to the
Glauconian epoch; _2dly_, because it still appears to me uncertain,
whether the species mentioned, Chondrites æqualis and intricatus, are
quite identical, specifically with the species of this name belonging
to the fucoidal sandstone lying above the chalk.
"III. REIGN OF THE ANGIOSPERMS.--The dominating character of this last
transformation of the vegetation of the globe, is the appearance of
Angiospermous dicotyledons, those vegetables which actually constitute
more than three-fourths of the vegetable creation of our epoch, and
which appear to have acquired this predominance from the commencement
of the Tertiary formations. For a long period I was of opinion that
these vegetables did not begin to appear till after the chalk, with
the earliest beds of the Tertiary formations; but more recent
investigation has shewn that beds belonging to the Chalk formation
present some very distinct examples.
"These vegetables appear even at the beginning of the Chalk formation;
for it is certain that many well-determined species exist in the
quadersandstein and planerkalk of Germany, which appear to correspond
to the green sandstone of France, or green sand of English geologists;
although this formation in France and England has never yielded any of
them, but only some examples of Cycadeæ, Coniferæ, and marine plants.
But in southern Sweden, at Kopingue in Scania, some specimens of
dicotyledonous leaves appear associated with a species of Cycadeæ, in
beds which have been referred to the greensand; so that the whole
Chalk formation would appear to constitute a first period in the reign
of the Angiosperms, forming, so to speak, the passage between the
vegetation of the Secondary and that of the Tertiary formations, still
presenting, as the first, a few Cycadeæ, as the following, some
Angiospermous dicotyledons, and thus paving the way to the
considerable development of these vegetables in the succeeding period.
This period is besides characterised by many Coniferæ peculiar to it,
and which appear very distinct from those of the Wealdean formations,
and from those of the Eocene epoch of the Tertiary formations; and
such in particular are the _Cunninghamites_.
"We can therefore distinguish two great periods in the reign of the
Angiosperms:
"_1st_, The Cretaceous period, a kind of period of transition.
"_2dly_, The Tertiary period, presenting all the characters arising
from the predominance of Angiosperms, Dicotyledons, and
Monocotyledons, and divisible into many epochs, the characters of
which will not be well established until we have removed all doubts as
to the agreement of the different local series of the Tertiary
formations.
"V. _Cretaceous Period._--The Cretaceous period, properly so called,
comprehends perhaps many distinct epochs; but the beds where fossil
vegetables have been observed, not having been always classified with
precision in the different subdivisions of this formation, it is
impossible to establish their chronology with certainty. Besides, we
must distinguish an epoch which appears immediately to precede this
formation, and one which follows it, and yet differs from the Eocene
period.
"We are acquainted with fossil vegetables of the Cretaceous period:--
"_1st, Sub-Cretaceous Epoch_.--In the subcretaceous marine lignites of
the Isle of Aix, near La Rochelle, and of Pialpinson, in the
department of the Dordogne; these are the most ancient beds of the
Cretaceous formation, or the last of the Jurassic period. Here have
been found only marine plants, wood, and branches of Coniferæ.
"_2d_, In the chloriteous chalk or greensand of southern England, the
neighbourhood of Beauvais and Maus; only Cycadeæ and marine plants
have been observed there.
"_3d_, In the same formation in Scania, where M. Nilson has observed
leaves of Dicotyledons mixed with leaves of Cycadites.
"_4th_, At Niederschoena, near Freyberg, in Saxony, beds, analogous to
greensand or quadersandstein, containing fossils of considerable
variety, Cycadeæ, Coniferæ, and Dicotyledons, particularly
_Credneria_.
"_5th_, In the quadersandstein of Bohemia and Silesia, at Blankenburg,
at Teifenfurth, Teschen, &c., where this sandstone is characterised by
the presence of dicotyledonous leaves of the genus _Credneria_, by
Cyeadeæ, and particularly by Coniferæ of considerable variety,
described by M. Corda in Reuss' work on the Chalk of Bohemia.
"_6th_, In France, in the iron sands connected with the green
sandstones, near Grand-Pré, in the department of Ardennes, where M.
Buvignier has found two fossil vegetables of a very remarkable
character, a stalk of an arborescent fern, and a cone previously
observed in England in the same formation.
"But in other places, and in beds belonging to epochs certainly
different, this period has presented only marine vegetables; such more
especially are those fucoidal sandstones or macigno, characterised by
Chondrites targionii, æqualis, intricatus, &c., now designated by the
name of fucoidal sandstone or flysch--the geological epoch of which
has long been doubtful, but which observers seem to agree in
considering as a distinct formation, superior to the chalk, and
inferior to the most ancient beds of the Tertiary formations.
"These fucoidal sandstones form a very distinct epoch, which hitherto
appears to be characterised only by marine vegetables, and what, at
least in a botanical point of view, would form the line of demarcation
between the Cretaceous and Tertiary formations; for it is remarkable
that the fuci found there in such great numbers have little connection
with those of the Chalk, properly so called, and none whatever with
those of the most ancient beds of the Tertiary formations, such as
those of Monte-Bolca.
"From the study and comparison of these fossils, derived from such
various sources, we may divide the Cretaceous period into three
epochs, of which the middle one is the true Cretaceous epoch. The
others, characterised almost exclusively by marine vegetables, are
somewhat doubtful with regard to their true geological position; the
one, more ancient than the Chalk, contains only the subcretaceous
lignites of the neighbourhood of La Rochelle, and the Department of
Dordogne; the other, superior to the Chalk, corresponds to the
Sandstone with fucoides."
The _subcretaceous_ epoch comprehends Algæ, Naiadeæ, and Coniferæ.
"This small Flora is almost entirely founded on fossil plants,
collected among the marine lignites of the Isle of Aix, near La
Rochelle, long since described by M. Fleureau de Bellevue.
"The difference of the vegetables does not appear to admit of
connecting this Flora with that of the inferior chalk or greensand;
but it would require to be more completely examined, both with regard
to its precise geological epoch and the entire amount of vegetable
species which it contains. The most abundant and characteristic of
these species is the _Rhodomelites strictus_, whose branches, crossed
and mingled with _Zosterites_, constitute the mass of these lignites
with the wood of Coniferæ, which have not yet been studied, and small
branchlets, very rare, of _Brachyphyllum orbignianum_.
"I have referred to this period the two _Cystoseirites_, described by
M. de Sternberg, and mentioned by him as found in the beds between the
jurassic slates and the chalk in Transylvania.
"Does this fossil Flora correspond to a formation almost entirely
marine, but cotemporary with the Wealdean epoch? New investigations
can alone determine this, but we may suppose an analogy between the
Brachyphyllum of the epochs."
_2d_, _Cretaceous Epoch_.--The Cretaceous epoch presents us, among the
amphigenous cryptogams, with Algæ, some of which are doubtful; among
the Acrogenous cryptogams, with ferns; the Monoctyledons are here
represented by two species of palms; the Gymnospermous dicotyledons by
the cycadeæ and coniferæ; the Angiospermous dicotyledons by a species
of Acerineæ, a betulaceæ, a cupulifera, salicineæ, an acerineæ, and a
juglandeæ; lastly, a few dicotyledons remain, but the determination of
the families to which they belong is uncertain.
"We ought, moreover, to notice at least from ten to twelve species of
dicotyledonous leaves, indeterminate, and often imperfect, figured by
Geinitz, Reuss, Corda, and Goeppert, or existing in collections.
"This Flora, which contains from sixty to seventy species, is, as we
perceive, remarkable in this respect, that the Angiospermous
dicotyledons nearly equal the Gymnospermous dicotyledons, and in the
existence of a pretty considerable number of well characterised
Cycadeæ, which cease to appear at the Eocene epoch of the Tertiary
formations.
"The genus _Credneria_, containing dicotyledonous leaves, with a very
peculiar nervation, but the affinities of which are doubtful, is
likewise one of the characteristic forms of this epoch, in a pretty
considerable number of localities. With regard to the species of
dicotyledonous leaves, referred to determined families, I may remark
that these supposed relations, founded on very imperfect specimens,
and very few in number, are still very uncertain, and incapable of
furnishing a basis for comparison with the other Floras, nor any
certain conclusion.
"_3d_, _Fucoidian Epoch_.--This epoch, which seems to me to form the
most natural limit between the Cretaceous and Tertiary periods, is
characterised by those deposits, so rich in Algæ, of a very peculiar
form, that they have been called the sandstones or macignos à
fucoïdes, or the flysch of Switzerland,--a formation very widely
spread, especially in southern Europe, from the Pyrenees, as far as
the vicinity of Vienna, and even to the Crimea.
"I have not hitherto found land plants mingled with these marine
species. I do not believe that fossil woods have been met with.
"Almost all these Algæ appear to belong to the same group, the genus
_Chondrites_; and although the species are pretty numerous, they pass
from one to another by almost insensible shades. The Algæ of the
neighbourhood of Vienna, placed in the genus _Munsteria_, are very ill
characterised, and perhaps are not congenerous with those of the
jurassic limestone of Solenhofen; but they appear to me to have been
found in the same formation, designated by the name of gray calcareous
slate, of the sandstone of Vienna, as the Chondrites of the same
country."
The Flora of the fucoidean sandstone is constituted by twelve species
of Algæ (_Chondrites_ and _Munsteria_.)
"What is remarkable in this series of species is, that they have
nothing in common, either with the Algæ of the Subcretaceous epoch, or
with those of the Eocene epoch, and particularly of Monte-Bolca, with
which this Flora should be almost cotemporary, according to many
geologists. The identity of these species of Algæ is likewise
remarkable in all the localities, however distant from each
other--localities so numerous, in regard to the greater number of
these species, that I have been unable to enumerate them.
"The Chondrites targionii, or perhaps a distinct species, but very
nearly related, is the only one presented in another formation, in the
greensand and gault of the Isle of Wight, in England, according to M.
Fitton; and in this same formation, in the department of the Oise,
according to M. Graves.
"M. Kurr has likewise described and figured, under the name of
_Chondrites bollensis_, a fucus of the Lias--the very varied forms of
which are almost identical with the Chondrites targionii, æqualis, and
difformis.
"VI. _Tertiary Period._--Considered as a whole, the vegetables of this
period, cotemporary with all the Tertiary deposits, and continued even
in the vegetation which now covers the earth's surface, is one of the
best characterised. The abundance of Angiospermous dicotyledons, that
of the monocotyledons of diverse families, but especially the Palms,
during a part at least of this period, immediately distinguish it from
the most ancient periods. Yet the observations made on the Cretaceous
epoch have established a kind of transition between the forms of the
Secondary epochs and those of the Tertiary epochs, which was not
suspected a few years ago. But while, at this period, the Angiosperms
appear nearly to equal the Gymnosperms, in the Tertiary period, they
greatly exceed them; while at the Cretaceous epoch, there are still
Cycadeæ and Coniferæ allied to the genera inhabiting tropical regions;
during the Tertiary period, the Cycadeæ appear to have been completely
wanting in Europe, and the Coniferæ belong to the genera of the
temperate regions.
"Notwithstanding this assemblage of characters common to the whole
Tertiary period, there are evidently notable differences in the
generic and specific forms, and in the predominance of certain
families at different epochs of this long period; but here we often
experience serious difficulties in establishing a uniformity as to
time among the numerous local formations which constitute the
different Tertiary formations. In assigning the different localities
where fossil vegetables have been observed to the principal divisions
of the Tertiary series, I have not followed exactly the bases admitted
by M. Unger in his Synopsis; I have approached nearer to the
distribution adopted by M. Raulin, in his Memoir on the
Transformations of the Flora of Central Europe during the Tertiary
period (Ann. Sc. Nat., t. x., p. 193, Oct. 1848), which refers many of
the formations, classified by M. Unger in the Miocene division, to the
Pliocene, or most recent epoch. Yet, according to the advice of M.
Elie de Beaumont, I have not placed all the Lignite formations of
Germany in the Pliocene division, as M. Raulin has done, nor all of
them in the Miocene division, like M. Unger; but, conformably to the
old opinion of my father, I have left the Lignites from the shores of
the Baltic, which include amber, in the inferior division of the old
basins of Paris, London, and Brussels, considering them cotemporary
with the Soisson Lignites. Those of the banks of the Rhine, of
Wetteravia and Westphalia, are arranged in the Miocene division; those
of Styria, and part of Bohemia, on the contrary, are placed among the
recent or Pliocene formations.
"This distribution agrees pretty generally with the nature of the
vegetables contained in them. One important point only leaves me in
doubt: this relates to the Lignites of the environs of Frankfort or
Wetteravia, the plants of which are pretty generally analogous to
those of OEningen or Partschlug in Styria; although their geological
position seems to call upon us to refer them to a more ancient
formation.