. Elementary botany. Botany. 194 MORPHOLOG Y. 393. Sporangia.—On examining the fruiting spike, we find as in lycopodium that there is but a single sporangium in the axil of a fertile leaf. But we see that they are of two different kinds, small ones in the axils of the upper leaves, and large ones in the axils of a few of the lower leaves of the spike. The micro- spores are borne in the smaller spore-cases and the macrospores in the larger ones. Figures 241-243 give the details. There are many microspores in a single small spore-case, but 3-4 ma- crospores in a large spore-case. 394. Male proth
. Elementary botany. Botany. 194 MORPHOLOG Y. 393. Sporangia.—On examining the fruiting spike, we find as in lycopodium that there is but a single sporangium in the axil of a fertile leaf. But we see that they are of two different kinds, small ones in the axils of the upper leaves, and large ones in the axils of a few of the lower leaves of the spike. The micro- spores are borne in the smaller spore-cases and the macrospores in the larger ones. Figures 241-243 give the details. There are many microspores in a single small spore-case, but 3-4 ma- crospores in a large spore-case. 394. Male prothallia.—The prothallia of selaginella are much reduced structures. The microspores when mature are already divided into two cells. When they grow into the mature pro- thallium a few more cells are formed, and some of the inner ones form the spermatozoids, as seen in fig. 244. Here we see that. Fig. 244. Details of microspore and male prothallium of selaginella; ist, microspore; 2d, wall re- moved to show small prothallial cell below; 3d, mature male prothallium still within the wall; 4th, small cell below is the prothallial cell, the remainder is antheridium with wall and four sperm cells within; 5th spermatozoid. After Beliaieff and Pfeffer. the antheridium itself is larger than the prothallia. Only an- theridia are developed on the prothallia formed from the microspores, and for this reason the prothallia are called male prothallia. In fact a male prothallium of selaginella is nearly all antheridium, so reduced has the gametophyte become here. 395. Female prothallia.—The female prothallia are devel- oped from the macrospores. The macrospores when mature have a rough, thick, hard wall. The female prothallium begins to develop inside of the macrospore before it leaves the sporangium. The protoplasm is richer near the wall of the spore and at the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - col
Size: 2614px × 956px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisher, booksubjectbotany
