Part 7

In this reign the Acrogenous species are less numerous; the Gymnosperms almost equal them in number, and ordinarily surpass them in frequency. There are two periods in this reign, one in which Coniferæ predominate, while Cycadaceæ scarcely appear; and another in which the latter family preponderates as regards the number of species, and the frequency and variety of generic forms. Cycadaceæ occupied a more important place in the ancient than in the present vegetable world. They extend more or less from the Trias formation up to the Tertiary. They are rare in the Grès bigarré or lower strata of the Triassic system. They attain their maximum in the Lias and Oolite, in each of which upwards of 40 species have been enumerated, and they disappear in the Tertiary formations. Schimper describes 13 genera of fossil Zamiæ, and about 20 Cycadeæ. He thinks that Trigonocarpum (15 species), Rhabdocarpum (24 species), Cardiocarpum (21 species), and Carpolithes (9 species), are all fruits of Cycadeæ. Many supposed fossil Cycads are looked upon by Carruthers as Coniferæ. Zamia macrocephala, or Zamites macrocephalus, or Zamiostrobus macrocephalus, is called by him Pinites macrocephalus; Zamia ovata, or Zamites ovatus, or Zamiostrobus ovatus, is Pinites ovatus; Zamia Sussexiensis is Pinites Sussexiensis. Among other species of Pinites noticed by Carruthers are Pinites oblongus, P. Benstedi, P. Dunkeri, P. Mantellii, P. patens, P. Fittoni, P. elongatus. It is important to notice that in an existing Cycad called Stangeria paradoxa the veins of the pinnæ rise from a true midrib and fork, characters which render untenable the distinction usually relied upon between the foliage of Ferns and Cycads.

[Sidenote: Fig. 76. _Schizoneura heterophylla_, one of the fossil Coniferæ of the Triassic system.]

In Brongniart's Vosgesian period, the Grès bigarré, or the Red Sandstones and Conglomerates of the Triassic system, there is a change in the flora. Sigillarias and Lepidodendrons disappear, and in their place we meet with Gymnosperms, belonging to the genera Voltzia, Haidingera, Zamites, Ctenis, Æthophyllum, and Schizoneura (Fig. 76). The genus Voltzia is confined to the Trias, and though a true conifer, it is not easy to correlate it with any living form. It is apparently Abietineous, having two seeds to each scale, but they are placed on the dilated upper portion of the scale. The leaves are of two kinds, the one broad and short, and the other at the tops of the branches long and linear. Species of Neuropteris, Pecopteris, and other acrogenous coal genera are still found, along with species of Anomopteris and Crematopteris--peculiar Fern-forms, which are not found in later formations. Stems of arborescent Ferns are more frequent than in the next period.

The Jurassic period of Brongniart embraces the Keupric period or variegated marls of the Triassic system, the Liassic epoch, the Oolitic and the Wealden. The flora of the Keupric epoch differs from that of the Grès bigarré of the Vosges. The Acrogens are changed as regards species, and frequently in their genera. Thus we have the genera Camptopteris, Sagenopteris, and Equisetum. Among Gymnosperms, the genera Pterophyllum and Taxodites occur.

[Sidenote: Figs. 77 to 81. Cycadaceæ of the Jurassic epoch of Brongniart, and of the Oolite. Fig. 77. Zamites, one of the fossil Cycadaceæ. Fig. 78. _Pterophyllum Pleiningerii_, leaf of a fossil Cycad. Fig. 79. _Nilssonia compta_ (_Pterophyllum comptum_ of Lindley and Hutton), from the Oolite of Scarborough. Lower part of the pinnatifid leaf, with blunt almost square divisions. There are numerous veins, slightly varying in thickness; while in Pterophyllum there are numerous veins of equal thickness, in Cycadites there is a solitary vein forming a thick midrib. Fig. 80. _Palæozamia pectinata_ (_Zamia pectinata_ of Brongniart, and Lindley and Hutton), a pinnated leaf, with a slender rachis. The pinnæ are linear, somewhat obtuse, with slender equal ribs. It is found in the Oolite of Stonesfield (Lindley and Hutton).]

In the Lias the essential characters of the flora are the predominance of Cycadaceæ, in the form of species of Cycadites, Otozamites, Zamites (Fig. 77), Ctenis, Pterophyllum (Fig. 78), and Nilssonia (Fig. 79), Palæozamia (Fig. 80), and the existence among the Ferns of many genera with reticulated venation, such as Camptopteris and Thaumatopteris, some of which began to appear at the Keupric epoch. Coniferous genera, as Brachyphyllum (Fig. 81), Taxodites, Palissya, and Peuce, are found. In the Lias near Cromarty, Miller states that he found a cone with long bracts like those of Pinus bracteata.

_FLORA OF THE OOLITIC EPOCH._

In the Oolitic epoch the flora consists of numerous Cycadaceæ and Coniferæ, some of them having peculiar forms. Its distinctive characters are, the rarity of Ferns with reticulated venation, which are so numerous in the Lias, the frequency of the Cycadaceous genera Otozamites and Zamites, which are most analogous to those now existing; the occurrence of a remarkable group presenting very anomalous structure in their organs of reproduction, to which Carruthers has given the name of Williamsonia; and the diminution of Ctenis, Pterophyllum, Palæozamia, and Nilssonia, genera far removed from the living kinds; and lastly, the greater frequency of the coniferous genera, Brachyphyllum and Thuites, which are much more rare in the Lias. In the Scottish Oolite at Helmsdale, Miller detected about 60 species of plants, including Cycadaceæ and Coniferæ, with detached cones, and Fern-forms resembling Scolopendrium. He also discovered a species of Equisetum, and what he supposed to be a Calamite.

[Sidenote: Fig. 81. _Brachyphyllum mammillare_, a Coniferous plant of the Oolitic system, Yorkshire.

Fig. 82. _Equisetum columnare_, a fossil species of the Oolite of Yorkshire.]

[Sidenote: Fig. 83. _Araucarites sphærocarpus_, Carr., found in the inferior Oolite at Bruton, Somersetshire.

Fig. 84. Termination of a scale of _Araucarites sphærocarpus_, Carr.

Fig. 85. Section of a scale of _Araucarites sphærocarpus_, Carr., showing the size and position of the seed.]

[Sidenote: Fig. 86. The _Dirt-bed_ of the Island of Portland, containing stumps of fossil Cycadaceæ in an erect position.

Fig. 87. _Cycadoidea megalophylla_ (_Mantellia nidiformis_ of Brongniart), a subglobose depressed trunk, with a concave apex, and with the remains of the petioles disposed in a spiral manner, the markings being transversely elliptical. It is found in the Oolite of the Island of Portland, in a silicified state.]

There is an absence of true coal-fields in the secondary formations generally; but in some of the Oolitic series, as in the lower Oolite at Brora, in Sutherlandshire, and in the north-east of Yorkshire, and the Kimmeridge clay of the upper Oolite, near Weymouth, there are considerable deposits of carbonaceous matter, sometimes forming seams of coal which have been worked for economic purposes.[19] Some suppose that the Brora coal was formed chiefly by Equisetum columnare (Fig. 82). In the sandstones and shales of the Oolitic series, especially in the lower Oolite of the north of England, as at Whitby and Scarborough, as well as in Stonesfield slate, the Portland Crag of the middle, and the Portland beds of the upper Oolite, numerous fossil plants are found. Peuce Lindleyana is one of the Coniferæ of the lower Oolite. Beania (Plate II. Fig. 2) is a Cycadaceous fossil from the Oolite of Yorkshire (Carruthers, Geol. Mag. vi. 91). Araucarites sphærocarpus (Figs. 83, 84, 85) is found in the inferior Oolite, and separate scales of Araucarian fruits occur in the Oolitic shales of Yorkshire (Araucarites Phillipsii, Plate II. Fig. 11), and in the "slate" at Stonesfield (A. Brodiei, Plate II. Fig. 10). The upper Oolite at Portland contains an interesting bed, about a foot in thickness, of a dark brown substance. This is the _Dirt-bed_ (Fig. 86) made up of black loam, which, during the Purbeck period, formed a surface soil which was penetrated by the roots of trees, fragments of whose stems are now found in it fossilised. These consist of an assemblage of silicified stumps or stools of large trees, from 1-3 feet high, standing in their original position, with the roots remaining attached to them, and still penetrating the earth in which they grew. Besides the erect trunks many stems have been broken and thrown down, and are buried in a horizontal position in the bed. They belong to Coniferæ and Cycadaceæ. One of these is Mantellia nidiformis, shown in Fig. 87. Carpolithes conicus and C. Bucklandi are fruits found in the Oolite. Some look upon them as fruits of palms.

[Sidenote: Fig. 88. _Kaidacarpum ooliticum_, Carr., fruit of a fossil allied to Pandanaceæ, from the great Oolite near Northampton.

Fig. 89. _Pandanus odoratissimus_, Screw-pine, with adventitious roots.]

Several species of Pandanaceous fruits have been found in Oolitic strata. Buckland described one of them as Podocarya, which is remarkable, as it consists of a single but many-seeded drupe. To another form, more nearly allied to the existing plants, Carruthers has given the name Kaidacarpum, and has described three species. These fruits are made up of a large number of single-seeded drupes. The species figured (Fig. 88) is from the great Oolite, near Northampton. In Fig. 89 a representation is given of one of the Pandanaceæ, the screw-pines of the present day.

_FLORA OF THE WEALDEN EPOCH._

[Sidenote: Fig. 90. Fossil Wood, _Abietites Linkii_. A Coniferous plant from the Wealden, showing punctated woody tissue and medullary rays.]

The flora of the Wealden epoch is characterised in the south of England by the abundance of the fern called Lonchopteris Mantellii, and in Germany by the predominance of the Conifer denominated Abietites Linkii (Fig. 90), and the presence of Araucarites Pippingfordensis, as well as by numerous Cycadaceæ, such as species of Cycadites, Zamites, Pterophyllum, Mantellia, Bucklandia, and a remarkable genus having a fleshy fruit, and related to the ordinary Cycadaceæ as Taxus is to the other Coniferæ, which has been fully described in the Linn. Trans., under the name of Bennettites (Plate II. Fig. 3). In the Wealden at Brook Point, Isle of Wight, Cycads have been detected allied to Encephalartos. The fruits of them are described by Carruthers as Cycadeostrobus. He describes the following species:--Cycadeostrobus ovatus (Plate II. Fig. 1), C. truncatus, C. tumidus, C. elegans, C. Walkeri, C. sphæricus, in the Oxford clay of Wiltshire; C. primævus in the inferior Oolite at Burcott Wood and Livingston, and C. Brunonis. Mantell states that he has found 40 or 50 fossil cones in the Wealden of England; they belong either to the genus Cycadeostrobus or to the pines mentioned below as occurring in the Wealden. The Wealden fresh-water formation terminates the reign of Gymnosperms. Carruthers gives the following list of the remains of Coniferæ which have been found in the secondary strata of Britain, excluding the Trias:--

Upper Chalk.--Wood in flint nodules.

Upper Greensand.--Foliage and cone of Sequoiites Woodwardii; cone of Pinites oblongus.

Gault.--Cones of Pinites gracilis and P. hexagonus, Sequoiites Gardneri and S. ovalis.

Lower Greensand.--Water-worn and bored pieces of wood; cones of Pinites Benstedi, P. Sussexiensis, and P. Leckenbyi.

Wealden.--Driftwood, foliage of Abietites Linkii; cones of Pinites Dunkeri, P. Mantellii, P. patens, and P. Fittoni, and of Araucaria Pippingfordensis; foliage (and drupes?) of Thuites Kurrianus.

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.

[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.

[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.

[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).

[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._

[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.]