. Morphology of gymnosperms. Gymnosperms; Plant morphology. 174 MORPHOLOGY OF GYMNOSPERMS regarded as a unique feature among gymnosperms until the terminal and erect microsporangia of Cycadofilicales were discovered. The Calymmatotheca type of stamen bears a terminal and erect synangium, in which the sporangia occur in various degrees of "; If such sporangia should fail to organize a synangium and should remain separate, such a stamen as that of Cordaitales would be the result. THE MEGASPORANGIUM The young ovulate strobilus can scarcely be distinguished from the staminate
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 174 MORPHOLOGY OF GYMNOSPERMS regarded as a unique feature among gymnosperms until the terminal and erect microsporangia of Cycadofilicales were discovered. The Calymmatotheca type of stamen bears a terminal and erect synangium, in which the sporangia occur in various degrees of "; If such sporangia should fail to organize a synangium and should remain separate, such a stamen as that of Cordaitales would be the result. THE MEGASPORANGIUM The young ovulate strobilus can scarcely be distinguished from the staminate, the ovules at that stage being completely hidden by the overlapping bracts. Renault's description (3) of Cordaianthus Williamsonii will illustrate the structure of the strobilus (fig. 207). Upon a thick conical axis con- spicuous bracts are inserted in spiral succession, and in some of their axils there arises a very short dwarf branch which bears some small bractlets and a terminal ovule. The ovule (fig. 208) has two integuments, the outer one being described as thick and fleshy, the inner one delicate but later be- coming hard. The two integuments are free from one another below, but are more or less united above. They may correspond to the outer fleshy and stony layers of the single integument of cycads and Ginkgo. There is nothing to indicate the presence of an inner fleshy layer. The nucellus is nearly distinct from the integument, and develops a prominent beak which contains a large pollen chamber. A single vascular strand enters the chalaza and sends out two systems of branches, one into the outer integument, and the other into the peripheral region of the nucellus. The freedom of integument and nucellus, and the occurrence of the inner set of vascular strands in the nucellus, are the striking features of the Stephanospermum type of seed, as. Fig. 206.—Cordaianthus Penjonii: section showing three stamens with their sporangia; the stamen in the middle bears four spo-
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