. The essentials of botany. Botany. CORDAITALES AND GINKGOALES 275 494. The Conifer Ancestors of the Paleozoic period (Order Cordaitales) were large trees 30 or more meters in height, and bearing a dense crown of branches and large, parallel-veined leaves, sometimes a meter or so in length. Microspore and megaspore cones are known, and even the seeds have been preserved, and many of their details of structure made Fig. 151.—Cordaites. Fig. 152.—Ginkgo (staminate and ovulate). 495. The Maidenhair Trees (Order Ginkgoales) re- mind one in some respects of the preceding. They were common in
. The essentials of botany. Botany. CORDAITALES AND GINKGOALES 275 494. The Conifer Ancestors of the Paleozoic period (Order Cordaitales) were large trees 30 or more meters in height, and bearing a dense crown of branches and large, parallel-veined leaves, sometimes a meter or so in length. Microspore and megaspore cones are known, and even the seeds have been preserved, and many of their details of structure made Fig. 151.—Cordaites. Fig. 152.—Ginkgo (staminate and ovulate). 495. The Maidenhair Trees (Order Ginkgoales) re- mind one in some respects of the preceding. They were common in the Mesozoic period, but all are now extinct excepting a single species {Ginkgo biloba) from eastern Asia. They have parallel-veined, fan-shaped leaves, and branching, woody stems. In the surviving species the trees are dioecious. The bisporangiate micro- sporophylls constitute a loose cone, while the mega- sporophylls remind one of those of Cycas described above. The seed integument becomes fleshy externally and stony internally when mature. 496. The Joint-firs (Order Gnetales), including several rather widely separated farhihes, should probably be placed here, although their relationship is doubtful, especially since they have non-ciliated sperms. Ephedra is a widely distributed genus of green, branching, leafless shrubs resembling Equisetum in appearance. Gnetum includes tropical shrubs and trees with large pinnately veined leaves; Tumboa (Welwitschia) occurs in tropical west Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bessey, Charles E. (Charles Edwin), 1845-1915; Bessey, Ernst Athearn, 1877-1957. joint author. New York, H. Holt and company
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