. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 420 MOSSES AND FERNS CHAP. than in Pilularia (Fig. 245, A, y). The next division is not always the same, but is usually effected by a wall nearly parallel to the first one, but more or less concave (Fig. 244, D). Some- times the antheridial cell divides at once by an oblique wall into two nearly equal cells, from each of which a group of sperm cells is later cut off. In no case was the central cell cut off by a dome-shaped wall, such as is common in the homosporous Ferns, and also in Pilularia
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 420 MOSSES AND FERNS CHAP. than in Pilularia (Fig. 245, A, y). The next division is not always the same, but is usually effected by a wall nearly parallel to the first one, but more or less concave (Fig. 244, D). Some- times the antheridial cell divides at once by an oblique wall into two nearly equal cells, from each of which a group of sperm cells is later cut off. In no case was the central cell cut off by a dome-shaped wall, such as is common in the homosporous Ferns, and also in Pilularia. The formation of this wall is apparently suppressed here, perhaps as the result of the ex- tremely rapid development of the antheridium, and the separa- tion of the sperm cells takes place by walls cut off from the periphery of the two,upper cells. A cap cell (Fig. 245, d) is almost always prese/t, as in Pilularia and the Polypodiacese. From the two cells of the middle part of the antheridium a varying number of sterile cells are cut off, which are quite transparent, while the contents of the central cells are very densely granular. Not infrequent- ly the two groups of sperm cells are completely separated by one of these sterile cells (Fig. 244, F), and Belajeff considers that each group of sperm cells represents a distinct antheridium. In view of the relationship between the Marsiliacese and Schizasacese, indicated by recent studies on the structure and development of the two families (Camp- bell (26)), this view has some support, as there is a cer- tain resemblance between each of these cell groups and the simple antheridium of Aneimia or Schizcea. The divisions in the central cells are very regular, and the sixteen sperm cells in each group are arranged very symmetrically (Fig. 245). The whole number in M. vestita is completed in about seven hours from the time germination begins, and the formation of the spermatozoids commences about an hour later and takes about. Fig. 24
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