404 



BOTANY OF THE LIVING PLANT 



tain fine-grained protoplasm and are shut off by a septum. The 

 sporangium is readily detached and germinates directly if the circum- 



Fig. 302. 



Portion of tissue near d in Fig. 300, highly magnified. The hyphae are seen 

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

 L> about to form. (After Marshall Ward.) 



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

 may directly infect a new victim. In other circumstances the ger- 

 minating filament may expand into a spherical body, and the contents 



Fig. 303. 



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

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

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

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



passing into it undergo division into a number of zoospores capable of 

 movement (Fig. 303). These escape by rupture of the vesicle as 

 minute colourless, kidney-shaped bodies with two active cilia. 

 Provided water is present, they can swim to and even climb up the 

 stem of other seedlings, and, coming to rest, perforate the superficial 



