SEXUAL REPRODUCTION 77 



Gametophyte. The vegetative hyphae 

 bearing zoosporangia 

 and sexual organs. 



I I 



Oogonium. Antheridium. 



Oosphere, with ovum nucleus. Fertilising tube with male nucleus. 



Oospore. Uninucleate. 



Sporophyte. Resting oospore, multi- 

 | nucleate. 



Sporangium. Each nucleus of sporo- 

 phyte divides to form 

 the nuclei of four 

 spores. 



Zoospores. 



Gametophyte. 



In- Cystopus bliti^ according to Stevens, the general 

 phenomena of fertilisation agree with those in Cystopus 

 cindidus, with the exception that the ooplasm of the 

 oogonium contains numerous nuclei. The antheridial 

 tube liberates about one hundred nuclei into the 

 oogonium, and these fuse in pairs with the female 

 nuclei. This results in the presence of numerous fusion 

 nuclei in the oosphere in place of one, as in Cystopus 

 candidus. Stevens calls this structure a compound 

 oosphere. The fusion nuclei remain throughout the 

 winter unchanged. 



Other species of Cystopus have been examined having 

 a smaller number of fusion nuclei in the oospore than 

 in Cystopus bliti; in fact there appears to be a sequence of 

 species of Cystopus ranging, so far as numbers of fusion 

 nuclei present in the oospore is concerned, from Cystopus 

 bliti with its numerous nuclei to Cystopus candidus ^ where 



