THE ALG^E 157 



enclosing membrane, swarm actively for a time, and 

 then come to rest, each giving rise to an ordinary 

 (Edogonium plant. It appears that in many cases the 

 plants remain through the winter in the state of young 

 filaments of three or four cells. Their contents 

 gradually assume the usual green colour. In a few 

 exceptional cases the oospore grows out directly into a 

 filament, and the contents of an unfertilised oogonium 

 sometimes behave in the same way. In other cases 

 again the contents divide as usual, but each of the cells 

 germinates directly within the oospore, without passing 

 through the swarming stage. All these cases, however, 

 are exceptions; the regular process is the production from 

 the oospore of the four zoospores, each of which gives 

 rise to a new plant. 



We have now completed the life - history of this 

 remarkable Alga. In what way can we compare it 

 with that of the higher Cryptogams ? One thing 

 is evident; we have here no such clear and regular 

 alternation of generations as we have hitherto found. 

 We cannot draw any sharp distinction between the 

 asexual and sexual individuals, for in most cases the 

 male and female plants themselves give rise also to the 

 asexual zoospores. On the other hand, we may regard 

 the germinating oospore, producing four asexual repro- 

 ductive cells, as representing an extremely simple 

 sporophytic generation. The oospore, however, is in 

 some cases capable of direct germination into a new 

 plant, which is as if the fertilised ovum of a Moss were 

 to grow out directly into a Moss-plant without form- 

 ing a spore-fruit. It is evident that the well-marked 

 alternation of generations by which all the higher plants 

 are characterised has not yet been established in Algte 



