Part 14

Purbeck.--Fossil forest in situ at Isle of Portland; cone "nearly related to Araucaria excelsa" in the Dirt-bed.

Portland Stone.--Driftwood Araucarites.

Kimmeridge Clay.--Cone of Pinites depressus.

Oxford Clay.--Driftwood and foliage of Araucarites.

Great Oolite.--Driftwood of Araucarites; foliage of Thuites acutifolius, T. articulatus, T. cupressiformis, T. divaricatus, and T. expansus, and of Taxites podocarpoides; detached cones at Helmsdale, Sutherland.

Inferior Oolite.--Wood of Peuce Eggensis (Tertiary according to 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.

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. 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.

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.

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).

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. 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.

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. 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.