PHYCOMYCETES. (a) OOMYCETES 



415 



ends oi the hyphae, by their swelling to an oval form, their storage 

 with fine-grained protoplasm, and being shut off by a septum. The 



FIG. 350. 



Portion of tissue near d in Fig. 348, highly magnified. The hyphae are seen 

 running in all directions ; at a, one passes through a stoma ; at c, a sporangium is 

 about to form. (After Marshall Ward.) 



sporangium is readily detached, and germinates directly if the circum- 

 stances are favourable. It then grows out into a fresh hypha, which 

 may directly infect a new victim. If one is not within reach, the 

 germinating filament may expand into a spherical zoo-sporangium, 



FIG. 351. 



Germination of a sporangium of Pythium debaryanum in water. The tube put 

 forth at a begins to swell at the end (6, c), and dilates (d), receiving all the protoplasm, 

 which rapidly breaks up into zoospores (). The whole process occupies about a 

 quarter of an hour. Highly magnified. (After Marshall Ward.) 



and the contents passing into it undergo division into a number 

 of zoo-spores capable of movement (Fig. 351). These escape by 

 rupture of the wall as minute colourless, kidney-shaped bodies with 

 two active cilia. Provided there is water as the medium, they can 



