64 



MOSSES 



stalk. The wall of the neck is composed of a single layer 

 of cells and the venter of two layers. The wall incloses one 

 layer of neck cells which dissolves to form mucilage when the 

 egg is mature. The egg is a large spherical cell contained 

 within the venter. 



x 



FIG. 30. Mosses. Gametophyte of polytricum. 



Fertilization. Antherozoids enter the neck of the arche- 

 gonium but only one unites with the egg cell to form the 

 beginning of the sporophyte plant. This cell remains in the 

 archegonium and is nourished by it. By repeated division 

 a sporophyte or asexual plant is formed. 



