The structure & development of the mosses and ferns (Archegoniatae) . When the antheridium arises at the endof a filament, the divisions in the terminal cell are very muchlike those in Osmunda. In the mother cell three intersectingwalls enclose a tetrahedral cell, which then has the cover cellcut off by a periclinal wall. In both forms of antheridium thesubsequent history is the same. The central cell divides firstby a transverse wall, followed by vertical walls in each cell, andsubsequently by numerous divisions which show no definitearrangement (Fig. 221, C), and produce a very large number
The structure & development of the mosses and ferns (Archegoniatae) . When the antheridium arises at the endof a filament, the divisions in the terminal cell are very muchlike those in Osmunda. In the mother cell three intersectingwalls enclose a tetrahedral cell, which then has the cover cellcut off by a periclinal wall. In both forms of antheridium thesubsequent history is the same. The central cell divides firstby a transverse wall, followed by vertical walls in each cell, andsubsequently by numerous divisions which show no definitearrangement (Fig. 221, C), and produce a very large number ofsperm cells. In the cover cell only radial walls are formed, and XIII EQUISETINE^ 427 it thus remains single-layered, as in Maratiia and is often a triangular opercular cell (Fig. 221, D, 0), re-calling the similar cell in these forms. Development of tJic Spennatozoids The large size of the spermatozoids of Equisetinn makesthem especially suitable for the study of their development, andthis was traced with some care in E. telinateia. The material. Fig. 222.—Development of the spermatozoids, X looo. A, Three of the central cells of an antheridunnbefore the final division; B-E, final nuclear divisions in the sperm cells; F-J, development ofthe spermatozoid from the nucleus of the sperm cell; c, the cilia ; K, two free spermatozoids ; r,the vesicle. used was fixed with i per cent chromic acid, stained with alum-cochineal, and microtome sections were then examined in Canadabalsam. The nuclei of the sperm cells previous to their finaldivision are globular and show one, sometimes two, small but dis-tinct nucleoli, and numerous chromosomes. In exceptional casesthe two directive spheres could also be seen. Previous tothe final division the latter take their place on opposite sides ofthe now somewhat flattened nucleus, whose nucleolus cannot bedistinguished and whose nuclear segments are very distinct, 428 MOSSES AND FERNS chap. short, curved bodies. Their number cou
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
