[BA] “Journal of the Geological Society,” London, 1881.
[BB] “Sphenopteris Refracta,” Goeppert; “Flora des Uebergangsgebirges.” “Cladoxylon Mirabile,” Unger; “Palæontologie des Thuringer Waldes.”
The history of the ferns in geological time is remarkably different from that of the Lycopods; for while the latter have long ago descended from their pristine eminence to a very humble place in nature, the former still, in the southern hemisphere at least, retain their arboreal dimensions and ancient dominance.
The family of the Equisetaceæ, or mare’s-tails, was also represented by large species of Calamites and by Asterophyllites in the Erian; but, as its headquarters are in the Carboniferous, we may defer its consideration till the next chapter. (Figs. [27], [28].)
Passing over these for the present, we find that the flowering plants are represented in the Erian forests by at least two types of Gymnosperms, that of Taxineæ or yews, and an extinct family, that of the Cordaites (Figs. [30], [31]). The yew-trees are closely allied to the pines and spruces, and are often included with them in the family of Coniferæ. They differ, however, in the habit of producing berries or drupe-like fruits instead of cones, and there is some reason to believe that this was the habit of the Erian trees of this group, though their wood in some instances resembles rather that of the Araucaria, or Norfolk Island pine, than that of the modern yews. These trees are chiefly known to us by their mineralised trunks, which are often found like drift-wood on modern sand-banks embedded in the Erian sandstones or limestones. It often shows its structure in the most perfect manner in specimens penetrated by calcite or silica, or by pyrite, and in which the original woody matter has been resolved into anthracite or even into graphite. These trees have true woody tissues presenting that beautiful arrangement of pores or thin parts enclosed in cup-like discs, which is characteristic of the coniferous trees, and which is a great improvement on the barred tissue already referred to, affording a far more strong, tough, and durable wood, such as we have in our modern pines and yews ([Fig. 29]).
Fig. 29.—Dadoxylon Ouangondianum, an Erian conifer, A, Fragment showing Sternberg pith and wood; a, medullary sheath; b, pith; c, wood; d, section of pith, B, Wood-cell; a, hexagonal areole; b, pore, c, Longitudinal section of wood, showing, a, areolation, and b, medullary rays, D, Transverse section, showing, a, wood-cells, and b, limit of layer of growth, (B, C, D, highly magnified.)