Fig. 69.—Leaf Impression of Ginkgo from Mesozoic Rocks of Scotland
Fig. 70.—Showing Epidermis with Stomates from the lower side of the Leaf seen in [fig. 69]
e, Epidermis cells; s, stomates; v, long cells of epidermis lying over the veins.
In the Palæozoic the records are not so undoubted, but there is strong evidence which leads us to suppose that if the genus now living were not then extant, at least other closely related genera were, and there seems to be good grounds for supposing that Ginkgo and Cordaites may have both arisen from some ancient common stock.
CHAPTER X
PAST HISTORIES OF PLANT FAMILIES
III. The Bennettitales
This fascinating family is known only from the fossils, and is so remote in its organization from any common living forms that it may perhaps be a little difficult for those who do not know the Cycads to appreciate the position of Bennettites. It would probably be better for one studying fossil plants for the first time to read the chapters on the Cycads, Pteridosperms, and Ferns before this chapter on the present group, which has characters connecting it with that series.
Until recently the bulk of the fossils which are found as impressions of stems and foliage of this family were very naturally classed as Cycads. They are extremely common in the Mesozoic rocks (the so-called Age of Cycads), and in the external appearance of both stems and leaves they are practically identical with the Cycads.
A few incomplete fructifications of some species have been known in Europe for many years, but it is only recently that they have been fully known. This is owing to Wieland’s[12] work on the American species, which has made known the complete organization of the fructifications from a mass of rich and well-petrified material.