. Morphology of gymnosperms. Gymnosperms; Plant morphology. 78 MORPHOLOGY OF GYMNOSPERMS whole cycadophyte phylum, including even the Cycadales, and is one of its striking features. THE MEGASPORANGIUM If the microsporangiate structures of Bennettitales have advanced little beyond the fern level, no such claim can be made for the mega- sporangiate structures. They are not only remarkably different from the corre- sponding structures among Cycadofilicales, but they are even more different from those of the Cycadales. The description of Bennettites Gib- sonianus, as given by Careuthers (2), Solms
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 78 MORPHOLOGY OF GYMNOSPERMS whole cycadophyte phylum, including even the Cycadales, and is one of its striking features. THE MEGASPORANGIUM If the microsporangiate structures of Bennettitales have advanced little beyond the fern level, no such claim can be made for the mega- sporangiate structures. They are not only remarkably different from the corre- sponding structures among Cycadofilicales, but they are even more different from those of the Cycadales. The description of Bennettites Gib- sonianus, as given by Careuthers (2), Solms-Laubach (s, 6), and Scott (10), may be used as an introduction to the situation (fig. 63). From the convex surface of the hemispherical receptacle a great number of slender stalks arise, which pass vertically upward, or diverge slightly toward the curved surface of the "; The central stalks are the longest, the outer ones gradually diminishing in length, so that the general outline is oblong or obovate. Each of these stalks bears at its tip a single erect seed, with the micro- pyle directed outward. The seeds are so placed that the long axis meets the sur- face approximately at right angles. The spaces among the stalks are packed with scales, which are dilated at tip, between the seeds, so as to form a continuous en- velope, interrupted only by the small pits through which themicropylartubesproject. The corresponding structures of the beautifully preserved Cycade- oidea Wielandii (fig. 64) have been more fully described by Wieland (22). They conform to the description of Bennettites given above, but many additional details are given. In the lower part of the ovuUf-. FiG. 62.—Cycadeoidea do cotensis: longitudinal section of synangium, showing stalk, hard outer layer of cells, por- tions of wall layers of cells, and two chambers containing pollen grains; X 40.—After Wieland (22).. Please note that these images are extracted from scanned page images that may h
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