Geikie); foliage of Brachyphyllum mammillare, Cryptomerites?
divaricatus, and Palissya? Williamsonis; cones of Araucarites
sphærocarpus, A. Brodiei, and A. Phillipsii. Pinites primæva
(Lindl. and Hutt.) is a Cycadean fruit.
Lias.--Wood of Pinites Huttonianus and P. Lindleyanus; foliage
of Araucaria peregrina and Cupressus latifolia; cone of Pinites
elongatus, and "cone with long bracts like those of Pinus
bracteata," from Cromarty.
Carruthers gives the following arrangement of fossil Cycadaceæ in
the Transactions of the Linn. Soc. vol. xxvi.--Firstly, the Cycadeæ:
including the genus Bucklandia, Presl; and species B. anomala, B.
Mantellii, B. squamosa, B. Milleriana--the two first-named species
being from the Wealden, and the two last-named from the Oolite.
Secondly, the Zamieæ: including the genus Yatesia, Carr.; and
species Y. Morrisi, Lower Cretaceous; Y. gracilis, Lias; Y. crassa,
M. Oolite; Y. Joassiana, M. Oolite; the genus Fittonia, Carr., and
species F. squamata, U. Cretaceous; the genus Crossozamia, Pomel,
and species C. Moreaui, Pomel, Jurassic, and C. Buvignieri, Pomel,
Jurassic--both from St. Michel, France. Thirdly, the Williamsonieæ:
including the genus Williamsonia, Carr.; and species W. gigas, W.
pecten, W. hastula, all from the inferior Oolite. Fourthly, the
Bennettiteæ: including the genus Bennettites, Carr., and species
B. Saxbyanus, Wealden; B. Gibsonianus, Lr. Greensand; B. maximus,
Wealden; B. Portlandicus, Lr. Purbeck; and B. Peachianus, M.
Oolite; the genus Mantellia, Brong., and species M. nidiformis, M.
intermedia, M. microphylla, from the Lr. Purbeck; and M. inclusa,
from the Lr. Cretaceous; the genus Raumeria, Goeppert, and species R.
Reichenbachiana, from Galicia, and R. Schulziana from Silesia.
FOSSIL FLORA OF THE TERTIARY OR CAINOZOIC PERIOD,
(INCLUDING THE CRETACEOUS EPOCH).
REIGN OF ANGIOSPERMS.
This reign is characterised by the appearance of Angiospermous
Dicotyledons, plants which constitute more than three-fourths of the
species of the existing flowering plants of the globe, and which
appear to have acquired the predominance from the commencement of the
Tertiary epoch. They are plants with seeds contained in seed-vessels,
and each seed with two cotyledons. These plants, however, appear even
at the beginning of the Cretaceous period. In this reign, therefore,
Brongniart includes the upper Secondary period, or the Cretaceous
system, and all the Tertiary period. The Cretaceous may be considered
as a sort of transition period between the reign of Gymnosperms and
Angiosperms.
_FLORA OF THE CHALK._
The Chalk flora is characterised by the Gymnospermous almost
equalling the Angiospermous Dicotyledons, and by the existence of a
considerable number of Cycadaceæ, which do not appear in the Tertiary
period. The genus Credneria is one of the characteristic forms. In
this period we find Algæ represented by Cystoseirites, Confervites,
Sargassites, and Chondrites; Ferns by peculiar species of Pecopteris
and Protopteris; Naiadaceæ by Zosterites; Palms, by Flabellaria and
Palmacites; Cycadaceæ by Cycadites, Zamites, Microzamia, Fittonia,
and Bennettites; Coniferæ, by Brachyphyllum, Widdringtonites,
Cryptomeria, Abietites, Pinites, Cunninghamites, Dammarites,
Araucarites; and Angiospermous Dicotyledons, by Comptonites, Alnites,
Carpinites, Salicites, Acerites, Juglandites, and Credneria. At the
base of the Tertiary period there are deposits of Algæ of a very
peculiar form, belonging to the genera Chondrites and Munsteria. No
land plants have been found mingled with these marine species.
[Illustration: Fig. 91.]
[Sidenote: Fig. 91. _Sequoiites ovalis._ Large cone.]
In the Gault, near Folkestone, an interesting association of
coniferous fruits has been found, consisting of two species of
Sequoia, along with two of Pinus. The pines belong to the same group
as those which now grow with the Wellingtonias in California, showing
the remarkable fact that the coniferous vegetation of the high lands
of the Upper Cretaceous period had a _facies_ similar to that now
existing in the mountains on the west of North America. We figure
both the species of Sequoiites--viz. S. ovalis (Fig. 91), a large
cone, and S. Gardneri (Plate II. Fig. 7). In the present day there
are two species of the genus Sequoia--viz. S. gigantea (Wellingtonia
gigantea) and S. sempervirens.[20] In the Lower Greensand a
remarkably fine cone belonging to the same group as the Cedar has
been found. This is the Pinites Leckenbyi (Plate II. Fig. 4). A
section exhibits the seeds in their true position, some of which are
preserved so as to exhibit the form and position of the embryo.
[Illustration: Fig. 92.]
[Sidenote: Fig. 92. _Pinites ovatus_ (_Zamia ovata_ of Lindley and
Hutton), an ovate cone with a truncated base and obtuse apex, nearly
allied to the stone-pine.]
The Tertiary period is characterised by the abundance of
Angiospermous Dicotyledons and of Monocotyledons, more especially of
Palms. By this it is distinguished from the more ancient periods.
Angiosperms at this period greatly exceed Gymnosperms. Cycadaceæ
are very rare, if not completely wanting, in the European Tertiary
strata, and the Coniferæ belong to genera of the temperate regions.
In the lower Tertiaries Carruthers has found a fossil Osmunda, and
the existence of a group of Pines having cones with a very thick
apophysis. From their remarkable external aspect, these cones
had been considered to be Cycadean, but their internal structure
indicates that they are coniferous. Pinites ovatus is one of
these cones (Fig. 92). The Cupressineæ are found in the Tertiary
beds only. Taxodieæ are represented by Sequoiites (Plate II. Fig.
7) in the Cretaceous and Eocene strata. Peuce australis of Van
Diemen's Land and P. Pritchardi of Ireland are Tertiary plants.
The Peuce of Eigg (P. Eggensis), according to Geikie, is also
Tertiary, and not Oolitic. Isoetes is mentioned by Schimper as a
Tertiary genus. Although the vegetation throughout the whole of the
Tertiary period presents pretty uniform characters, still there
are notable differences in the generic and specific forms, and in
the predominance of certain orders at different epochs. Brongniart
does not entirely agree with Unger as to these epochs. Many of the
formations classified by Unger in the Miocene division he refers with
Raulin to the Pliocene. He divides the Tertiary period, as regards
plants, into the Eocene, Miocene, and Pliocene epochs, and gives the
following comparative results from an examination of their floras:--
+-----------------+---------------+----------------+-----------------+
| Classes and | | | |
| Sub-Classes. | Eocene Epoch. | Miocene Epoch. | Pliocene Epoch. |
+-----------------+---------------+----------------+-----------------+
| Thallogenæ | 16 | 6 | 6 |
| Acrogenæ | 17 | 4 | 7 |
| Monocotyledones | 33 | 26 | 4 |
| Dicotyledones-- | | | |
| Gymnospermæ | 40 | 19 | 31 |
| Angiospermæ | 103 | 78 | 164 |
+-----------------+---------------+----------------+-----------------+
| | 209 | 133 | 212 |
+-----------------+---------------+----------------+-----------------+
_FLORA OF THE EOCENE EPOCH._
In the Eocene formation the fossil fruits of the Isle of Sheppey
increase the number of Phanerogamous plants, only a small proportion
of which have as yet been described. This is an exceptional locality,
and the deposit in which the fruits occur is probably the silt found
at the mouth of a large river which flowed, like the Nile, from
tropical regions towards the north. The number of plants as given by
Brongniart is much smaller than that mentioned by Unger (p. 23). The
latter includes in his enumeration a considerable amount of uncertain
species.
[Illustration: Fig. 93.]
[Sidenote: Fig. 93. _Palmacites Lamanonis_. Fan-shaped (flabellate)
leaf of a Palm.]
The Eocene epoch in general is characterised by the predominance of
Algæ and marine Naiadaceæ, such as Caulinites and Zosterites; by
numerous Coniferæ, the greater part resembling existing genera among
the Cupressineæ, and appearing in the form of Juniperites, Thuites,
Cupressinites (Plate II. Figs. 8, 9), Callitrites, Frenelites, and
Solenostrobus; by the existence of a number of extra-European forms,
especially of fruits, such as Nipadites, Leguminosites, Cucumites,
and Hightea; and by the presence of some large species of Palm
belonging to the genera Flabellaria and Palmacites (Fig. 93).
[Illustration: Fig. 94.]
[Sidenote: Fig. 94. _Osmunda regalis_, Royal Fern, having a bipinnate
frond and fructification in a spike-like form, the branches bearing
sporangia.]
Unger says that the Eocene flora has resembled in many respects that
of the present Australian vegetation. He gives the following genera
as occurring at the Eocene epoch:--Araucaria, Podocarpus, Libocedrus,
Callitris, Casuarina, Pterocarpus, Drepanocarpus, Centrolobium,
Dalbergia, Cassia, Cæsalpinia, Bauhinia, Copaifera, Entada, Acacia,
Mimosa, Inga. (Seemann's Journal of Bot. vol. iii. p. 43.) Amber is
considered to be the produce of many Coniferæ of this epoch, such
as Peuce succinifera or Pinites succinifera, and Pinus Rinkianus. It
occurs in East Prussia in great quantity, and it is said that many
pieces of fossil wood occur there, which, when moderately heated,
give out a decided smell of amber. Connected with these beds are
found cones belonging to Pinites sylvestrina and P. Pumilio-miocena,
species nearly allied to the living species; others to Pinites
Thomasianus and P. brachylepis. Goeppert contrasts the present flora
of Germany and that of the Amber epoch as follows:--
German Flora. Amber Flora.
Cryptogameæ 6800 60
Phanerogameæ 3454 102
and gives the following specimens of two of the orders:--
Cupuliferæ 12 10
Ericaceæ 23 24
(See remarks by Goeppert on the Amber Flora, etc., Edin. N. Phil.
Journ. lvi. 368; and Quart. Journ. Geol. Soc. x. 37.) In the lower
Eocene of Herne Bay, Carruthers noticed a fern like Osmunda (Fig.
94), which he calls Osmundites Dowkeri (Plate I. Figs. 8, 9). This
specimen was silicified; starch grains contained in its cells, and
the mycelium of a parasitic fungus traversing some of them, were
perfectly preserved. Berkeley has detected in amber fossil fungi,
which he has named Penicillium curtipes, Brachycladium Thomasinum,
and Streptothrix spiralis.[21] Some Characeæ are also met with, as
Chara medicaginula and C. prisca, with a fossil called Gyrogonites,
the nucule or the fructification of these plants. Carpolithes ovatus,
a minute seed-vessel, occurs in the Eocene beds of Lewisham. Another
small fruit, of a similar nature, called Folliculites minutulus,
occurs in the Bovey Tracey coal, which belongs to the Tertiary beds.
_FLORA OF THE MIOCENE EPOCH._
[Illustration: Fig. 95.]
[Sidenote: Fig. 95. _Comptonia acutiloba_, apparently the leaf of
a plant belonging to the natural order Proteaceæ, which abound in
Australia, and are also found at the Cape of Good Hope at the present
day.]
[Sidenote: Figures 96 to 99 show the leaves of plants belonging to
the Miocene epoch.]
[Illustration: Fig. 96-97.]
[Illustration: Fig. 98.]
[Sidenote: Fig. 96. _Acer trilobatum_, a three-lobed palmate leaf,
like that of the Maple, with the lobes unequal, inciso-dentate, the
lateral ones spreading, found at Œningen. Fig. 97. _Ulmus Bronnii_,
a petiolate leaf, like that of the Elm, unequally ovato-acuminate,
feather-veined and toothed, found in Bohemia. Fig. 98. _Rhamnus
Aizoon_, a petiolate elliptical obtuse feather-veined leaf, with an
entire margin, found in Styria.]
The most striking characters of the Miocene epoch consist in the
mixture of exotic forms of warm regions with those of temperate
climates. Unger says that it resembles that of the southern part
of North America. Thus we meet with Palms, such as species of
Flabellaria and Phœnicites, a kind of Bamboo called Bambusium
sepultum; Lauraceæ, as Daphnogene and Laurus; Combretaceæ, as
Getonia and Terminalia; Leguminosæ, as Phaseolites, Desmodophyllum,
Dolichites, Erythrina, Bauhinia, Mimosites, and Acacia--all plants
having their living representatives in warm climates; Echitonium,
Plumiera, and other Apocynaceæ of equatorial regions; Comptonia (Fig.
95), a Proteaceous genus, and Steinhauera, a Cinchonaceous genus;
mingled with species of Acer (Fig. 96), Ulmus (Fig. 97), Rhamnus
(Fig. 98); and Amentiferous forms, such as Myrica, Betula, Alnus
(Fig. 99), Quercus, Fagus, Carpinus, all belonging to temperate
and cold climates. The statements as to the occurrence of Pinus
sylvestris and Betula alba among the Miocene fossils have not been
founded on complete data. It is by no means easy, even in the present
day, to distinguish fragments of dried specimens of Pinus Pumilio
from those of P. sylvestris, and from a great many other Pines.
The difficulty is still greater in fossils (Hook. Kew Journ. v.
413). There are a very small number of plants belonging to orders
with gamopetalous corollas. In the Miocene formation of Lough
Neagh in Ireland, and of Mull in Scotland, silicified trunks of
considerable size have been found. The Irish silicified wood has been
denominated Cupressoxylon Pritchardi from its apparent resemblance
to the Cypress. As connected with the Miocene epoch, we may notice
the leaf-beds found at Ardtun, in the island of Mull, by the Duke
of Argyll.[22] Above and below these beds basalt occurs, and there
are peculiar tuff-beds alternating with the leafy deposits. These
tuff-beds were formed by the deposit of volcanic dust in pools
probably of fresh water. They contain fragments of chalk and flint.
The leaves are those of plants allied to the Yew, Rhamnus, Plane, and
Alder, along with the fronds of a peculiar Fern, and the stems of an
Equisetum. The genera are Taxites or Taxodites (Fig. 100), Rhamnites
(Fig. 101), Platanites, Alnites, Filicites, and Equisetum (Fig.
102). In the leaf-beds at Bournemouth Mr. Wanklyn detected several
ferns. One is a species of Didymosorus, and shows distinct venation
and fructification. Fossilised wood was found in the Arctic Regions
by Captain M'Clure. At the N.W. of Banks Land he found trees with
trunks 1 foot 7 inches in diameter.
[Illustration: Fig. 99-101.]
[Sidenote: Fig. 99. _Alnus gracilis_, an ovate-oblong leaf, like that
of the Alder, found in Bohemia.]
[Sidenote: Figures 100, 101, 102, exhibit fragments of plants which
occur in the leaf-bed at Ardtun Head, in Mull, and which is referred
to the Miocene epoch. The figures are from the Duke of Argyll's
paper.]
[Sidenote: Fig. 100. _Taxites_, or perhaps _Taxodites Campbellii_, a
branch with leaves resembling those of the Yew, or rather those of
Taxodium.
Fig. 101. _Rhamnites multinervatus_, a leaf resembling
that of Rhamnus.]
[Illustration: Fig. 102.]
[Sidenote: Fig. 102. _Equisetum Campbellii_, a stem like that of an
Equisetum of the present day.]
Dr. Oswald Heer[23] has examined the plants preserved in the lignite
beds of Bovey Tracey, in Devonshire, and he finds that they belong
to the Miocene formation. There is a remarkable coincidence between
this and several of the continental fossil floras, such as those
of Salzhauser in the Wetterau, Manosque in Provence, and of some
parts of Switzerland. Bovey Tracey has no species in common with
Iceland, although the Tertiary flora of Iceland belongs to the
same period. Two of its species (Corylus MacQuarrii and Platanus
aceroides) have been found in the Miocene of Ardtun Head. Even the
genera are distinct, with the exception of Sequoia and Quercus. The
Bovey Tracey flora has a much more southern character, corresponding
entirely with that of the Lower Miocene of Switzerland. It contains
three species of Cinnamon, one Laurel, evergreen Figs, one Palm, and
large Ferns, thus manifesting a subtropical climate. One of the most
important plants is Sequoia Couttsiæ, a Conifer which supplies a link
between S. Langsdorfii and S. Sternbergi, the widely-distributed
representatives of S. sempervirens and S. gigantea (Wellingtonia),
which are Californian trees. Among other characteristic plants may be
mentioned Cinnamomum lanceolatum and C. Scheuchzeri; Quercus Lyellii,
an evergreen oak; species of evergreen fig (Ficus Falconeri and F.
Pengellii), Palmacites Dæmonorops, a prickly twining Rotang-palm;
species of Vine (Vitis Hookeri and V. Britannica); Pecopteris
lignitum, a large tree-fern; species of Nyssa, at present confined
to North America. Among other plants recorded by Heer in his paper
are the following:--Laurus primigenia, Daphnogene Ungeri, species
of Dryandroides, Andromeda, Vaccinium acheronticum, Echitonium
cuspidatum, Gardenia Wetzleri, species of Anona, Nymphæa Doris,
Carpolithes Websteri, C. Boveyanus, and other species. In the
post-tertiary white clay of Bovey Tracey, Salix cinerea, and a
species allied to S. repens, as well as Betula nana, are found.
The Arctic fossil flora (Miocene), according to Heer, amounts to
162 species: Cryptogamia, 18 species, of which 9 are large ferns;
Phanerogamia, Coniferæ, 31; Monocotyledons, 14; Dicotyledons, 99.
Among the Coniferæ are--Pinus M'Clurii, Sequoia Langsdorffii,
Sternbergi, and Couttsiæ, Taxodium dubium, Glyptostrobus europæus,
Thujopsis europæa. Among leafy trees are--Fagus Deucalionis, Quercus
Olafseni, Platanus aceroides, willows, beeches, Acer, Otopteryx,
tulip-tree, walnuts, Magnolia Inglefieldi, Prunus Scottii, Tilia
Malmgreni, Corylus M'Quarrii, Alnus Kefersteinii, Daphnogene Kannii,
probably one of the Lauraceæ; and among Proteaceæ, MacClintockia? and
Hakea. In Greenland are found species of Rhamnus, Paliurus, Cornus,
Ilex, Cratægus, Andromeda, Myrica, Ivy, and Vine. From the flora of
Spitzbergen, in the Miocene epoch, we may conclude that under 79°
N. lat. the mean temperature of the year may have been 41° Fahr.,
while at the same epoch that of Switzerland was 69°·8 Fahr.; judging
from the analogy of floras, it appears that the mean temperature
has fallen 6°·9. From this it follows that at Spitzbergen, at
78° N. lat., the mean temperature was perhaps 41°·9 Fahr. In
Greenland, at 70°, it would be 49°·1 Fahr., and in Iceland and on
the Mackenzie, in lat. 65°, it would be 52°·7 Fahr. At the Miocene
epoch the temperature seems to have been much more uniform, the
mean heat diminishing much more gradually in proportion as the pole
was approached. The isothermal line of 32° Fahr. might have fallen
upon the pole, while now it is situated under 58° N. (See Heer's
conclusions as to changes of temperature depending on proportion
of sea and land, eccentricity of the earth, and the earth moving
through warm and cold spaces in the universe--Ann. Nat. Hist. 4th
ser. i. 66.)
In speaking of the Polar flora of former epochs, Heer says that every
plant executes a slow and continuous migration. These migrations,
the starting-point of which is the distant past, are recorded in
the rocks; and the interweaving of the carpets of flowers which
adorn our present creation retraces them for us in its turn. For
the vegetation of the present day is closely connected with that of
preceding epochs; and throughout all these vegetable creations reigns
_one_ thought, which not only reveals itself around us by thousands
upon thousands of images, but strikes us everywhere in the icy
regions of the extreme north. Organic nature may become impoverished
there, and even disappear when a cold mantle of ice extends over the
whole earth; but where the flowers die the rocks speak, and relate
the marvels of creation; they tell us that even in the most distant
countries, and in the remotest parts, nature was governed by the same
laws and the same harmony as immediately around us.[24]
_FLORA OF THE PLIOCENE EPOCH._
The flora of the Pliocene epoch has a great analogy to that of the
temperate regions of Europe, North America, and Japan. We meet with
Coniferæ, Amentiferæ, Rosaceæ, Leguminosæ, Rhamnaceæ, Aceraceæ,
Aquifoliaceæ, Ericaceæ, and many other orders. There is a small
number of Dicotyledons with gamopetalous corollas. The twenty
species with such corollas recognised by Brongniart are referred to
the Hypogynous Gamopetalous group of Exogens, which in the general
organisation of the flowers approach nearest to Dialypetalæ. In
this flora there is the predominance of Dicotyledons in number and
variety; there are few Monocotyledons. No species appear to be
identical, at least with the plants which now grow in Europe. Thus
the flora of Europe, even at the most recent geological epoch of the
Tertiary period, was very different from the European flora of the
present day.
Taking the natural orders which have at least four representatives,
Raulin[25] gives the following statement as to the Tertiary flora
of central Europe. The Eocene flora of Europe is composed of 128
species, of which 115 belong to Algæ, Characeæ, Pandanaceæ, Palmæ,
Naiadaceæ, Malvaceæ, Sapindaceæ, Proteaceæ, Papilionaceæ, and
Cupressineæ. The Miocene flora has 112 species, of which 69 belong to
Algæ, Palmæ, Naiadaceæ, Apocynaceæ, Aceraceæ, Lauraceæ, Papilionaceæ,
Platanaceæ, Quercineæ, Myricaceæ, and Abietineæ. The Pliocene
flora has 258 species, of which 226 belong to Algæ, Fungi, Musci,
Filices, Palmæ, Ericaceæ, Aquifoliaceæ, Aceraceæ, Ulmaceæ, Rhamnaceæ,
Papilionaceæ, Juglandaceæ, Salicaceæ, Quercineæ, Betulaceæ, Taxaceæ,
Cupressineæ, and Abietineæ. The Eocene species are included in
genera which belong at the present day to inter-tropical regions,
comprising in them India and the Asiatic islands of Australia. Some
are peculiar to the Mediterranean region. The aquatic plants, which
form almost one-third of the flora, belong to genera now peculiar to
the temperate regions of Europe and of North America, or occurring
everywhere. The Miocene species belong to genera, of which several
are found in India, tropical America, and the other inter-tropical
regions, but which for the most part inhabit the sub-tropical and
temperate regions, including the United States. Some of the genera
are peculiar to the temperate regions. The aquatic genera, poor in
species, occur everywhere, or else solely in the temperate regions.
The Pliocene species belong to genera which almost all inhabit the
temperate regions, either of the old continent or of the United
States. A few only are of genera existing in India, Japan, and the
north of Africa. These various floras, which present successively
the character of those of inter-tropical, sub-tropical, and
temperate regions, seem to indicate that central Europe has, since
the commencement of the Tertiary period, been subjected, during
the succession of time, to the influence of these three different
temperatures. It would appear, then, Raulin remarks, that the climate
of Europe has during the Tertiary period gradually become more
temperate.