. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 129 endosperm is differentiated into an endosperm jacket or tapetum as conspicuous as the tapetum of any fern or angiosperm microsporan- gium. In the mature seed the outer fleshy layer remains fresh for a while, and then either dries or decays. All the sporophytic tissue within the stony layer, including the irmer fleshy layer, the nucellus, and the base of the ovule, becomes reduced to a thin dry membrane in which the bundles of the inner vascular system are the most notice- able 123 124 Figs. 123-125.—Dioon edule
. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 129 endosperm is differentiated into an endosperm jacket or tapetum as conspicuous as the tapetum of any fern or angiosperm microsporan- gium. In the mature seed the outer fleshy layer remains fresh for a while, and then either dries or decays. All the sporophytic tissue within the stony layer, including the irmer fleshy layer, the nucellus, and the base of the ovule, becomes reduced to a thin dry membrane in which the bundles of the inner vascular system are the most notice- able 123 124 Figs. 123-125.—Dioon edule: photographs of ovules after allowing eosin to enter the bundles; fig. 123, vertical view shov\ring 14 bundles; the eosin has spread and exaggerated the size of the outer bundles; fig. 124, photographed after the endosperm and part of the inner fleshy layer had been removed; fig. 125, transverse section; s, stony layer; 0, outer fleshy layer, showing cut ends of bundles of outer vascular system; i, inner fleshy layer with bundles; », inner fleshy layer and fused portion of nucellus; c, endosperm; all X2.—After Chamberlain (46). The vascular anatomy of the ovule in its broader features is quite uniform throughout the group. There is an outer set of vascular strands, consisting of a few bundles, that traverses the outer fleshy layer of the integument and extends with little or no branching from the base of the ovule to the micropyle; and an inner set traversing the fleshy layer just within the stony coat, extending to the free portion of the nucellus, branching dichotomously, and often anastomosing. A general view of the two systems of bundles is shown in figs. 123- 125. After investigating all the genera except Microcycas and Cera- tozamm, Worsdell (27a) states that two bundles leave the vascular. 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
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