THE PTERIDOPHYTA : LYCOPSIDA, ETC. 



589 



Fertilization is effected by the passage of the antherozoids down the 

 neck of the archegonium, and the fusion of one male nucleus with that of 

 the oosphere. Prior to this the neck canal cells and the ventral canal cell have 

 disorganized. 



ARCHEGONIUM 



SUSPENSOR 



PRO-EMBRYO 



OOSPHERE 



SUSPENSOR 



PROTHALLUS 



WITH 

 ARCHEGONIA 



RESERVE TISSUE 



OF MEGASPORE 



PRO-EMBRYO 



Fig. 598. — Selaginella kraussiana showing development of the embryo from the 

 fertihzed oosphere, penetrating into the reserve tissue. {After Bruchmann.) 



Development of the Embryo 



After fertilization the oosphere becomes surrounded by a wall and may 

 then be regarded as an oospore. The oospore divides into two cells by a 



