128 MOSSES AND FERNS chap. 



first divisions, but his account of the apical grov/th, which he 

 supposed was due to a single apical cell, and the differentiation 

 of the archesporium, was shown by the careful investigation of 

 Leitgeb -^ to be erroneous. The following account is based 

 upon a large series of preparations of A. IcEvis and A.fusifo7'inis, 

 which seem to agree in all respects. After fecundation the 

 Q^^ at once develops a cellulose wall and begins to grow until 

 it completely fills the centre cavity of the archegonium. As it 

 grows the uniformly granular appearance of the cytoplasm dis- 

 appears, and large vacuoles are formed, so that the whole cell 

 appears much more transparent. The granular cytoplasm is 

 now mainly aggregated about the nucleus, which has also 

 increased in size (Fig. 57, E). The first division wall is parallel 

 with the axis of the archegonium and divides the embryo into 

 two equal parts, in which the character of the cells remains much 

 as in the undivided &%Z- Here too the granules are most 

 abundant about the nucleus, from which radiate plates that 

 separate the vacuoles. The next divisions are transverse and 

 divide the embryo into two upper large cells and two lower 

 smaller ones. The embryo at this stage is oval and more or 

 less pointed above. In each of the four primary cells vertical 

 walls arise that divide the embryo into octants, but the upper 

 octants are decidedly larger than the lower. Next, in the upper 

 cells, transverse walls are formed and the embryo then consists 

 of three tiers of four cells each. Of these the cells of the upper 

 tier are decidedly the larger. At this stage, in neither species 

 examined by me, were any traces present of the projection of 

 the basal cells figured by Leitgeb.^ As his drawings were 

 made from embryos that had been freed from the thallus, 

 probably with the aid of caustic potash, it is quite possible that 

 this appearance was due in part at least to the swelling of the 

 cell walls through the action of the potash. At any rate in 

 microtome sections of both species in these early stages, the 

 basal cells do not project in the least (Fig. 60, A). The next 

 divisions are very uniform in the upper tier of cells, from which 

 the capsule develops, but less so for the two lower ones. In 

 the upper tier, seen in cross-section (Fig. 60, B i), a slightly 

 curved wall running from the median wall to the periphery 

 forms in each quadrant, which thus viewed is divided into an 

 inner four-sided and an outer three-sided cell. In the former a 



1 Leitgeb (7), vol. v. ^ Leitgeb (7), vol. v. PI. I. 



