. Fundamentals of botany. Botany. 352 STRUCTURE AND LIFE HISTORIES ized into spores, which escape from the cell-wall of the mother-cell. In a number of many-celled plants (, Ulothrix) practically every protoplast has the capacity of becoming organized into one or more spores which escape from the old cell-cavity. The next higher step is the restriction of spore formation to certain cells in special organs (sporangia), while the other cells function only Fig. 261.—Woodwardia orientalis. Portion of a leaf bearing numerous young plantlets on its upper surface. 319. Cell-fusions
. Fundamentals of botany. Botany. 352 STRUCTURE AND LIFE HISTORIES ized into spores, which escape from the cell-wall of the mother-cell. In a number of many-celled plants (, Ulothrix) practically every protoplast has the capacity of becoming organized into one or more spores which escape from the old cell-cavity. The next higher step is the restriction of spore formation to certain cells in special organs (sporangia), while the other cells function only Fig. 261.—Woodwardia orientalis. Portion of a leaf bearing numerous young plantlets on its upper surface. 319. Cell-fusions.—Through all the variations of re- production by spores there is, as a rule, only the separation of protoplasts from the parent body, never a cell-fusion or nuclear-fusion. Some plants, however, such as Ulothrix (Fig. 262), have been found to produce two sizes of spores, and the small spores must always unite before they can develop into full-sized, mature individuals.^ Attention has already been called (Chapter XVIII) to the condition of similar sized gametes (isogamy)', as in Spirogyra, in contrast to that of unequal gametes {hetero- gamy), as in Ascophyllum and Fucus. ' In certain cases {, Ulothrix) the microspores may develop small, imperfect individuals without 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 not perfectly resemble the original Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's son & co.
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