. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. LEPTOSPORANGIATM HETEROSPORE^ 423 developed. A noticeable difference is the segregation of the protoplasm containing the nucleus, which occupies the apical papilla. This is filled with fine granules, but is entirely free from the very large starch grains of the large basal part of the spore. The nucleus is somewhat flattened. A similar arrange- ment of the spore contents is found in Pilularia, but the apex of the spore does not form a distinct papilla. The epispore is of nearly equal thickness
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. LEPTOSPORANGIATM HETEROSPORE^ 423 developed. A noticeable difference is the segregation of the protoplasm containing the nucleus, which occupies the apical papilla. This is filled with fine granules, but is entirely free from the very large starch grains of the large basal part of the spore. The nucleus is somewhat flattened. A similar arrange- ment of the spore contents is found in Pilularia, but the apex of the spore does not form a distinct papilla. The epispore is of nearly equal thickness, except at the extreme apex, in Mar- silia, but in Pilularia, especially in P. globulifera, the epispore. Fig. 248.—Marsilia vestita. Germination of the macrospore; A, longitudinal section of the ripe macrospore, X6o; «, nucleus; B-G, successive stages in the development of the female prothallium and archegonium, X360; C, E, transverse sections, the others longitudinal; n, neck canal cell; h, ventral canal cell; /, receptive spot of the egg; k, remains of the nucleus of the spore cavity. of the upper third is much thicker, and from the outside the spore appears somewhat constricted below this. Previous to the first division, which in M. vestita takes place about two hours after the spores are placed in water, the amount of protoplasm at the apex increases, and the nucleus becomes nearly globular and there is an increase in the amount of chromatin. In Pilularia the first wall is always transverse and cuts off the mother cell of the prothallium; but in Mar- silia, while this is usually so, occasionally a lateral cell is cut. 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 Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Company;
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