THE FERNS 



129 



phyte may be described as amphibious, inasmuch as it 

 must become aquatic, so to speak, in order that fertili- 

 zation may be effected. 



The spermatozoid, attracted by the substance ejected 

 from the open archegonium, swims to it and makes, its 

 way through the ■ 

 canal in the neck 

 to the central 

 cavity, where it 

 quickly pene- 

 trates the egg- 

 cell and slowly 

 fuses with its 

 nucleus, after 

 undergoing a se- 

 ries of changes. 

 As a result of 

 fertilization the 

 egg begins to 

 grow, having 

 in the mean 

 time secreted a 

 wall about itself, 

 and thus forms 

 what may be 

 called a spore, 



comparable to the resting-spore of such green algse as 

 (Edogonium, or to the fertilized egg-cell in the moss 

 archegonium. Like the latter it germinates at once 

 instead of passing through a long dormant period, as in 

 most green algse. 



The early divisions in the young embryo, developed 



Fig. 33. — A, the open archegonium of the ostrich- 

 fern, showing the egg-cell, o, within the venter; 

 B, the antheridium of the same species ; C, a 

 free spermatozoid, showing the numerous cilia ; 

 D, the fertilized archegoninm containing the 

 young embryo sporophyte ; E, the archegonium 

 of a liverwort, Riccia, with the young sporophyte, 

 showing the close resemblance between the ferns 

 and mosses in regard to the young sporophyte ; 

 F, longitudinal section of an older embryo of 

 the ostrich fern, showing the division into stem, 

 St; leaf, L; root, R; and foot, F. 



