124 



MOSSES AND FERNS 



CHAP. 



the apex none but radial walls are formed after the first trans- 

 verse wall has divided the body of the antheridium into two 

 tiers, and when complete the wall consists of three well-marked 

 transverse rows of cells, the lower being derived from the upper- 

 most tier of stalk cells. At the apex the cells are not quite so 

 regular (Figs. D, E). In its younger stages the antheridium 

 is very transparent and perfectly colourless. In each peripheral 

 cell a chloroplast is evident, but at this stage it is quite colour- 

 less and the nucleus is very easily seen in close contact with it. 



Fig. 58. — Ajithoccros fusifor7nis (Aust.)- Development of the antheridium ; D, E, drawn from 

 living specimens, the others microtome sections ; D, t, shows the single chloropla-st in each of the 

 wall cells;_and the secondary antheridium (s) budding out from its base ; 2 is an optical section 

 of the same ; E, surface view of fuU-gi^own antheridium ; F, cross-section of a younger one. Figs. 

 A, E X225, the others X450. 



As the antheridium grows the chloroplasts develop with it, 

 becoming much larger and elongated in shape, and at the same 

 time develop chlorophyll. The mature chloroplast is a flattened 

 plate that nearly covers one side of the cell, and its colour has 

 changed from green to a bright orange as in the antheridium 

 of many Mosses. The sperm cells are discharged through an 

 opening formed by the separation of the apical cells of the 

 antheridium. These cells do not become detached, and return 

 to their original position, so that the empty antheridium has its 



