. Morphology of gymnosperms. Gymnosperms; Plant morphology. GINKGO ALES 193 Cycadofilicales. The known stamens of Cordaitales are different (p. 172), but it cannot be supposed that the stamens of so great a group were uniform in type. In fact, in Antholithus Zeilleri, which is re- garded as the stami- nate strobilus of Bai- era (a mesozoic mem- ber of Ginkgoales), the sporangium-bearing structures are dichoto- mously divided, dorsi- ventral organs, the ultimate divisions of which bore eight sporangia (49). This structure seems to be widely different from the stamen of Ginkgo, so much so as to
. Morphology of gymnosperms. Gymnosperms; Plant morphology. GINKGO ALES 193 Cycadofilicales. The known stamens of Cordaitales are different (p. 172), but it cannot be supposed that the stamens of so great a group were uniform in type. In fact, in Antholithus Zeilleri, which is re- garded as the stami- nate strobilus of Bai- era (a mesozoic mem- ber of Ginkgoales), the sporangium-bearing structures are dichoto- mously divided, dorsi- ventral organs, the ultimate divisions of which bore eight sporangia (49). This structure seems to be widely different from the stamen of Ginkgo, so much so as to raise the question whether this Antholithus be- longs to Baiera, and hence to the Gink- goales; but if the sporangia are ter- minal, the parallel is found in the known stamens of Cordai- tales. If the sporangia are abaxial on the ultimate branches, rather than terminal, the reduction to a single branch would represent the stamen of Ginkgo. In either. Figs. 219—221.—Ginkgo hiloba: fig. 219, young staminate strobilus in September, showing microsporo- phylls with sporogenous tissue and mucilage ducts; X20; fig. 220, young sporangium; the four cells in which nuclei are shown have come doubtless from a single archesporial cell; the two inner cells are spo- rogenous and the two outer tapetal; X485; fig. 221, a rather late stage in the formation of a mucilage duct in the hump; the sporogenous-like ceUs are breaking down and the surrounding cells resemble a tapetum; X485.—After Miss Stare (53).. 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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