THE STORY TOLD BY FOSSIL PLANTS
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Fig. 5.—Restoration of Protolepidodendron, an upper Devonian ancestor of the subsequently differentiated forms of Lepidodendron and Sigillaria, the arborescent Palaeozoic club mosses. (After Berry.)
a, Lepidodendron-like leaf sears; b, Sigillaria-like leaf sears; c, leaf, about natural size.
a, Lepidodendron-like leaf sears; b, Sigillaria-like leaf sears; c, leaf, about natural size.
called the age of gymnosperms (plants with naked seeds, such as the pines), but it may perhaps be more properly called the age of cycads (Figs. 8 and 9), for its rocks contain cycad-like plants in great abundance and variety. The known Jurassic floras, whether of swamp or upland, consisted primarily of ferns, cycads, and conifers. The ferns were all forms of moderate size. None of the cycad-like forms that are so characteristic of that age of the earth’s history were tall; probably none were as tall as an old cycad of to-day. Rising above the general low level of these cycads were the various conifers,
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