202 



PRACTICAL BOTANY 



186. Increase in complexity of sex organs and gametes. It 



is to be especially noted that in other algae which we have 



studied reproduc- 

 tive bodies were 

 formed from cells 

 which at the out- 

 set were vegeta- 

 tive cells. In Vau- 

 cheria sex organs 

 are made primarily 

 for the work of 

 reproduction, an 

 interesting divi- 

 sion of labor in 

 the plant. In some 

 green algae, as 

 (Edogonium (Figs. 

 164 and 165), 

 vegetative cells 

 are thus formed 

 into oogonia and 

 antheridia. 



It is also im- 

 portant to note 

 that in Pleura- 

 coccus the entire 



plant might divide 

 A, holdfast cell and two vegetative cells; B, part of f f - i f 



a plant in which are an oogonium (o), containing egg, e V 



and two groups of antheridia (a), which have not yet 

 formed sperms ; (7, part of a plant in which is an oogo- 

 nium (o), which, by breaking away of one vegetative 

 cell, has made a place for the sperm to enter, so that a 

 fertilized egg or oospore has been formed, as is shown 

 by its heavy inner wall ; D, a zoospore of (Edogonium, 

 D redrawn from Pringsheim. All greatly enlarged 



FIG. 165. Reproduction in (Edogonium nodosum 



two new plants ; 

 or, in relatives 

 of Pleurococcus, 

 the entire plant 

 might become a 



spore case (spo- 

 rangium), producing zoospores. In Cladophora, zoospores are 

 formed, together with zoospore-like gametes, the latter uniting 



