202 MOSSES AND FERNS CHAP. 



below instead of truncate. The tetrahedral cell now divides 

 by a transverse wall into an upper cell, corresponding to the 

 "cover cell" of the Liverwort archegonium, and an inner one 

 (Fig. 105, A), which gives rise to the primary neck canal cell, 

 the egg, and the ventral canal cell. From this point, however, 

 the development proceeds in another way, and follows the 

 course observed in Andrecea. The cover cell, instead of divid- 

 ing by quadrant walls, has a regular series of segments cut off 

 from it, and acts as an apical cell. These segments are cut off 

 parallel both to its lateral faces and base, and thus form four 

 rows of segments, the three derived from the lateral faces 

 forming the outer neck cells, and the row of segments cut off 

 from the base constituting the axial row of neck canal cells. 

 Each row of lateral segments is divided by vertical walls, and 

 forms six rows, which later divide by transverse walls as well 

 so that the number of cells in each row exceeds the original 

 number of segments. This is not the case with the canal cells, 

 which, so far as could be determined, do not divide after they 

 are first formed. The wall of the venter owes its origin en- 

 tirely to the three peripheral cells formed by the other primary 

 walls in the archegonium mother cell. This becomes two-lay- 

 ered before the archegonium is mature, and is merged gradu- 

 ally into the massive pedicel, which in the Mosses generally is 

 much more developed than in the Hepaticse. In the older 

 archegonia the neck cells do not stand in vertical rows, but are 

 somewhat obliquely placed, owing to a torsion of the neck dur- 

 ing its elongation. From the central cell the ventral canal cell 

 is cut off, as usual, but is relatively smaller than is usual among 

 the Hepaticse. The egg shows a distinct receptive spot, which 

 is not, however, very large. The rest of the egg shows a 

 densely granular appearance, and the moderately large nucleus 

 shows very little colourable contents, beyond the large central 

 nucleolus. The terminal cells of the open archegonium diverge 

 widely, giving the neck of the archegonium a trumpet shape 

 (Fig. 105, F). Usually some of the cells become detached and 

 are thrown off. 



Holferty ( i ) has made a careful study of the archegonium 

 in Mnium cuspidatum and finds that the archegonium in its 

 earliest stages grows from a two-sided initial cell like that of 

 the antheridium. This is later replaced by the usual tetra- 

 hedral apical cell found in other species. After a more or less 



