. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 8o FECUNDATION; HETEROGAMETES. former. These plasmic rings or diaphragms communicate with each other by plasmic strands or bridges. In the plasmic rings are located the rounded chloroplasts, pyrenoids and the nuclei. Of the latter the number in each ring varies from 3 to 20 in var. braunii and from i to 4 in var. crassisepta (Fig. 27, A). In those cells in which spermatozoids are developed the nuclei undergo four or five karyokinetic divisions," so that ultimately about 300 small nuclei are present in each band (Fig.
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 8o FECUNDATION; HETEROGAMETES. former. These plasmic rings or diaphragms communicate with each other by plasmic strands or bridges. In the plasmic rings are located the rounded chloroplasts, pyrenoids and the nuclei. Of the latter the number in each ring varies from 3 to 20 in var. braunii and from i to 4 in var. crassisepta (Fig. 27, A). In those cells in which spermatozoids are developed the nuclei undergo four or five karyokinetic divisions," so that ultimately about 300 small nuclei are present in each band (Fig. 28, A to F). During these divisions the pyrenoids disappear, and the chromatophores undergo several divisions and assume a pale, yellowish-brown Fig. 57.—Cell-cleavage leading to formation of egg-cells in S^haroplea lraunii.—{,kilKC Klebahn.) A, outer view of a protoplasmic ring of a vegetative cell, showing chromatophores, pyrenoids and nuclei. B, portion of an oogonium showing frothy nature of protoplasm and early stages of cleavage. C, small portion of oogonium, showing irregular protoplasts resulting from cleavage, which contain several nuclei and pyrenoids. The plasmic rings up to this time retain their original form. Now the cytoplasm segments into numerous protoplasts, the spermatozoids, in such a manner that each spermatozoid receives only one nucleus (Fig. 29, I, J, K, L). The mature spermatozoids (var. crassiseftd) are as a rule spindle-shaped, being smaller at the anterior end, which bears the two cilia. Near the middle lies the very small and densely staining nucleus (Fig. 29, L). Kny in his Wandtafel, LXiii, figures four or five yellowish chromatophores in each spermatozoid. The processes leading to the formation of the egg-cells show a marked difference from those taking place in the antheridium. Even ' For details of karyokinesis see Klebahn, ' Please note that these images are extracted from scanned page images that may have been digitally enhan
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