Classification . 7 7 



formed in the oogonium ; several antlieridia are also 

 frequently present. In some species of Pythiitm tlie 

 gonoplasm can be distinctly seen to enter tlie oosphere, 

 whereas according to De Baiy, in the genus Fliytop- 

 thora, only a very minute quantity of protoplasm 

 passes from the antheridium into the oosphere, and 

 this portion is not previously differentiated into 

 gonoplasm^ while in the Bapr oh cj niece, according to 

 the same author, the fertilization-tubes of the 

 antheridia pierce the wall of the oogonia as in Pythium, 

 and come in contact with the oospheres, but never 

 open at the apex, hence no protoplasm passes from 

 the antheridium into the oogonium ; in other words, 

 fertilization does not take place, nevertheless, the 

 oospheres germinate as usual. 



In some species, as Pythium de Baryanum, the 

 oospores on germination put out a tube which directly 

 branches and forms a mycelium, which again produces 

 oogonia. In other instances, as in Cystopus candidus, 

 the germinating oospore produces zoospores, which 

 after a short period of activity become passive and 

 germinate, giving origin to a mycelium which pro- 

 duces oogonia. In a third group, including Pythium 

 gracile, some of the oospores give origin to germ-tubes 

 directly, whereas others produce zoospores. The 

 gonidial form of reproduction varies considerably in 

 different genera. A peculiar habit, characteristic of 

 Saprolecjniay but met with also in certain species of 

 Pythium, is as follows. The zoosporangia are terminal 

 cells separated from the cavity of the hypha by a 

 septum. After the zoogonidia have escaped from the 

 zoosporangium through an opening formed at the apex. 



