THE FERNS 



129 



D 



3- em 



phyte may be described as amphibious, inasmuch as it 

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

 zation maj T 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 



st 



Fin. 33. A, the open archegonium of the ostrich- 

 fcrn, 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 archegonium containing the 

 young embryo sporophyte ; E, the archegonium 

 of a liverwort, Riccia, with the young sporophyte, 

 showing the close resemblance between the ferns 

 and mossi's 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. 



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 



K 



