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.
Fig. 77.
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.
Fig. 78. Fig. 79.
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).
Fig. 80.