. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. EQUISETINE^ A77 characteristic nuclear plate. The separate nuclear spindles finally converge more and more, until finally they unite into a more or less definite large bipolar spindle with the nuclear plate at the equator (Fig. 279, C). Before the final division takes place, the sporogenous cells become completely rounded off, and are embedded in a mass of nucleated protoplasm (Fig. 280, A) derived from the tapetal cells, but also in part from some of the archesporial cells vi^hich do not deve
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. EQUISETINE^ A77 characteristic nuclear plate. The separate nuclear spindles finally converge more and more, until finally they unite into a more or less definite large bipolar spindle with the nuclear plate at the equator (Fig. 279, C). Before the final division takes place, the sporogenous cells become completely rounded off, and are embedded in a mass of nucleated protoplasm (Fig. 280, A) derived from the tapetal cells, but also in part from some of the archesporial cells vi^hich do not develop into spores. Fig. 279 shows the successive stages in the process. During. Fig. 279.—^A, Group of four sporogenous cells of H, telmateia, X400; B, C, first mitosis in E. Umosum (after Osterhout); B, shows the multipolar spindle; D, E, second mitosis in E. telmateia. the division of the primary nucleus there is an evident cell plate formed, but no division wall. During this first division there is probably a reduction in the number of the chromosomes, as in Osmunda. At any rate the number is evidently much smaller during the metaphases of the second nuclear divisions (Fig. 279, D). The second divisions are the same as the primary one, and the planes of the two nuclear spindles may either be parallel or at right angles (Fig. 279, D). In either case the resulting nuclei arrange themselves at equal distances from the. 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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