. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 454 OPHIOGLOSSALES corresponding in every other respect, do not assume the dense protoplasm of sporogenous cells. These more bulky sporangia lead on to such as that shown in Fig. 253 e, in which it is possible that the whole sporogenous group is referable to a single parent cell, though the proportions of the whole group are quite different from those of the typical sporangia; the sporogenous cells appear, however, to form two groups, and probably originated from two similar cells side by side. The in
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 454 OPHIOGLOSSALES corresponding in every other respect, do not assume the dense protoplasm of sporogenous cells. These more bulky sporangia lead on to such as that shown in Fig. 253 e, in which it is possible that the whole sporogenous group is referable to a single parent cell, though the proportions of the whole group are quite different from those of the typical sporangia; the sporogenous cells appear, however, to form two groups, and probably originated from two similar cells side by side. The interest of this lies in the fact that these broad sporangia approach. Fig. 253. Betryckium daitcifolium. Wall. A and C, successive stages of the most common type of sporangium. B= a small sporangium of narrow form. Z>=a very broad sporangium; the cells marked (jr) correspond to the sporogenous group, but showed no signs of developing further as such. E=3. still broader sporangium with wide sporogenous group, referable to two parent cells, possibly ultimately to one. F, G=synangia cut transversely and vertically. X 200. in their form and bulk to the synangia which, as above noted for Botrychium Lunaria, are not unfrequently found; one of these, cut through transversely, is shown in Fig. 253 f ; here there is a zone of three layers of sterile tissue forming a septum between the two sporogenous groups. The septum is, however, commonly broader than this: if a comparison be made between this and the young synangia of Tmesipteris the similarity will be readily seen. Such examples as these, which can easily be found in sections of the fertile spike, illustrate the gradual transitional forms which may be traced between the simpler and more complex spikes of the genus. Whether these steps will bear an evolu- tionary interpretation, as illustrating the manner of advance from a. Please note that these images are extracted from scanned page images that may have been digitally enhanced fo
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