. Foundations of Botany. Botany. 302 FOUNDATIONS OF BOTANY non-sexual generation, the sporophyte, often being of large size. The ferns (non-sexnal generation), for instance, are perennial plants, some of them tree- like. Some pteridophytes, as the Saivinia, a small floating aquatic plant, some- times known as a water-fern (Fig. 215), produce two kinds of spores, the large ones known as macrospores, and the small ones known as micro- spores (Fig. 216). Both kinds pro- duce microscopic prothallia, those of the former bearing only archegonia, those of the latter only antheridia. From the prothall
. Foundations of Botany. Botany. 302 FOUNDATIONS OF BOTANY non-sexual generation, the sporophyte, often being of large size. The ferns (non-sexnal generation), for instance, are perennial plants, some of them tree- like. Some pteridophytes, as the Saivinia, a small floating aquatic plant, some- times known as a water-fern (Fig. 215), produce two kinds of spores, the large ones known as macrospores, and the small ones known as micro- spores (Fig. 216). Both kinds pro- duce microscopic prothallia, those of the former bearing only archegonia, those of the latter only antheridia. From the prothallia of the macro- spores a plant (non-sexual generation) of considerable complexity of struc- ture is formed. 374. Parts of the Flower which correspond to Spores. — In seed-plants the spore-formation of cryptogams is repre- sented, though in a way not at all evident without careful explanation. The pistil is the macrospore-producing leaf or mac- rosporophyll, and the stamen is the microspore-producing leaf or micro sp or ophyll. Pines and other Saivinia. gymnosperms produce a large cell (the embryo sac) in the ovule (Fig. 217), which corresponds to the macrospore, and a pollen grain which represents the microspore. In its. Fig. 215.—A Water-Fern (Saivinia).. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & company
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