ISOETES 139 



embryo-sporophyte, that develops from the 

 fertilized egg. 



The archegonia are exposed for fertilization 

 by the splitting of the wall of the megaspore 

 along the ridges, but the prothallus itself does 

 not project beyond the walls of the spore. 



When the sporophyte begins to develop from 

 the fertilized egg, it continues to grow, without 

 any resting period, until it is mature. 

 Diagram the life cycle of Isoetes, as directed for 

 Marchantia. Let MG = male gametophyte; FG = 

 female gametophyte; 5 = sperm; e = egg; S = 

 sporophyte; mi = microspore; mg = megaspore. 



