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.
Fig. 81. Fig. 82.
Fig. 81. Brachyphyllum mammillare, a Coniferous plant of the Oolitic system, Yorkshire.
Fig. 82. Equisetum columnare, a fossil species of the Oolite of Yorkshire.
Fig.83. Fig. 85.
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.