DESCBIPTION OF PLATE V. 



(Pythium de Baryanum Hesse.) 



(All figures magnified 640 diameters.) 



Oogonium and antheridium during fertilisation. 



Oogonium and antheridium before fertilisation has commenced. 

 The antheridial cell already cut off. the oogonium still in communication 

 with the stalk hypha. 

 3 and 4. Early stages of oogonium and antheridium. 



Very early stage in the formation of the sexual organs. The more 

 curved branch becomes the oogonium, the other the antheridium. 



Two ripe oospores, showing antheridia still attached. 



An intercalar ripe oospore. 



Mycelium with sporangia, before the commencement of germina- 

 tion. 

 Fig. 9. Older mycelium with sporangia which have commenced to germin- 



ate by putting out beaks. 

 Fig. 10. Intercalar sporangia, showing irregular shapes. 



Fig. 11. Sporangium just prior to liberation of zoospores. The vacuole 



has disappeared and the tip of the beak is furnished with a hyaline cap. 

 Fig. 12. The same sporangium a few minutes later. The hyaline cap has 



blown out to a thin-walled bladder in which the protoplasm of the spo- 

 rangium has accumulated. 



Zoospores during the free swimming period. 



Zoospores after coming to rest and while the two cilia are being 

 retracted. 



Germination of the zoospores. 



A conidium shortly after germination. The germ-tube is beginning 

 to branch at its tip and part of the spore-contents have passed into it. 



