130 SEAWEEDS 



through the bursting of the apex. They gain access 

 to the oosphere by its apical opening and impregnate 

 it. The oospore thus formed invests itself with a 

 wall, assumes a brownish colour, and generally under- 

 goes a period of rest before germination. The plants 

 that result from this germination are commonly 

 reproduced by non-sexual means for several genera- 

 tions of individuals before antheridia and oogonia 

 are formed again. 



Zoosporangia, usually slightly club-shaped, are 

 produced by the formation of a cross-wall near the 

 end of a filament. The contents of the cell so formed, 

 which are rich in green colouring matter, gradually 

 contract into an oval shape, and escape by the 

 bursting of the wall at the apex. There is thus 

 normally but one zoospore in each zoosporangium, 

 and it is large and ciliated at all points, except in 

 some cases the posterior portion. These cilia are in 

 pairs, and immediately beneath each pair there is a 

 nucleus near the surface, as if the whole body 

 represented an aggregate of zoospores which have 

 failed to separate. In the formation of zoospores in 

 other Qhlorophycece, there is usually one formed for 

 each nucleus in the parent cell, and it is only natural 

 to regard the case of Vaucherw, in the light indicated, 

 as pointed out by Schmitz, who first observed it. It 

 is more than a mere case of preserving the multi- 

 nucleate character of the parent cell, since there is 

 this definite relation of nuclei to pairs of cilia. It 

 is of interest in this connection to note that during 

 the escape of this great zoospore it sometimes gets 

 nipped in two by the wall in passing the opening, and 



