. Morphology of gymnosperms. Gymnosperms; Plant morphology. GINKGOALES 189 observed is a reduction from the tetrarch condition. In the case of three cotyledons, which sometimes occurs in Ginkgo, the vascular situation is modified, so that the root is ultimately triarch. The testimony of the vascular anatomy shows that Ginkgo has departed farther from the primitive fern stock in this regard than have the Cycadales and the Cordaitales, only the foliar gaps and the mesarch bundles of the cotyledons remaining to indicate the connec- tion in vascular structure (36), THE LEAF There is great variatio
. Morphology of gymnosperms. Gymnosperms; Plant morphology. GINKGOALES 189 observed is a reduction from the tetrarch condition. In the case of three cotyledons, which sometimes occurs in Ginkgo, the vascular situation is modified, so that the root is ultimately triarch. The testimony of the vascular anatomy shows that Ginkgo has departed farther from the primitive fern stock in this regard than have the Cycadales and the Cordaitales, only the foliar gaps and the mesarch bundles of the cotyledons remaining to indicate the connec- tion in vascular structure (36), THE LEAF There is great variation in the size and in the lobing of the leaves of Ginkgo. The blades are often deeply cut and with more than two lobes, and the same tree may show every gradation between deeply. Fig. 214.—Baiera gracilis: leaf showing bilobed character, but each of the two principal lobes repeatedly dichotomous; regarded as a transition between Baiera and Ginkgo; natural size.—After Renault (qo). lobed leaves and those with nearly entire margins. The leaves of mesozoic species were much more divided, extreme forms being palmately dissected into numerous very narrow lobes (28) (fig. 214). In the surviving genus Ginkgo, the lobed condition is always found in the leaves of seedlings (fig. 215), and usually on the long shoots, leaves from the top of a tree being particularly deeply cleft. The leave's on the dwarf shoots are usually nearly entire, but when the bud of a dwarf shoot' develops into a long shoot, the lobed character of. 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 Coulter, John Merle, 1851-1928; Chamberlain, Charles Joseph, b. 1863; Coulter, John Merle, 1851-1928. Morphology of spermatophytes. Part I. Gymnosperms. Chicago, University of Chicago Press
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