Fig. 61.—Leaf of Cordaites, l, attached by its broad base to a Stem, s
We now know that Cordaites were large trees, with strong upright shafts of wood, to whose branches large simple leaves were attached. The leaves were much bigger than those of any living Gymnosperm, even than those of the Kauri Pine (a member of the Araucariaceæ), and seem in some species to have exceeded 3 ft. in length. The trees branched only at the top of the main shaft, and with their huge sword-like leaves must have differed greatly in appearance from any plant now living. The leaves had many parallel veins, as can be seen in [fig. 61], and were attached by a broad base directly to the main stem; thus coming closer to the Araucarias than the other groups of Gymnosperms in their leaf characters.
Fig. 62A.—Microscopic Section of Part of a Leaf of Cordaites
V, Vascular bundle; W, wood of bundle; sh, its sheath; S1, large sclerenchyma mass alternating with bundles; S2 and S3, sclerenchyma caps of bundle; P, soft tissue of leaf.
The internal anatomy is often well preserved, and there is a number of species of leaves whose anatomy is known. As will be expected from the parallel veins, in each section there are many vascular bundles running equidistantly through the tissue. [Fig. 62A] shows the microscopic details from a well-preserved leaf. In all the species patches of sclerenchyma were developed, and everything indicates that they were tough and well protected against loss of water, even to a greater extent than are most of the leaves of living Gymnosperms.
In the stems the pith was much larger than that in living Gymnosperms (where the wood is generally very solid), and it was hollow in older stems, except for discs of tissue across the cavity. The internal cast from these stems has been described before, and is seen in [fig. 63].
Fig. 62B.—Much-magnified Wood Elements from Cordaites Stem seen in longitudinal section, the type known as Araucarioxylon. Note the hexagonal outlines of the bordered pits, which lie in several rows