PARASITIC FUXGI 



9 



threads that run between the cells send into the cells 

 themselves little processes called "suckers," or haustoria, 

 which assist in absorbing the cell contents. Thus, in 

 the downy mildew of the grape this occurs in a way 

 illustrated at Fig. 7. Tliese threads running through 

 the leaf lead to the disorganization of its tissues, causing 

 the cells to collapse and turn brown. When they have 



FIG, 6. SURFACE OF POTATO LEAF GREATLY MAGNIFIED, SHOWING 

 GERMINATING SPORE ENTERING BREATHING PORE AT a, 

 AND GOING THROUGH EPIDERMIS AT C. 



developed to a considerable extent they collectively form 

 the mycelinm of the fungus. 



After the Peronospora plant has reached this stage 

 in its existence it is ready to prepare for reproduction. 

 It sends out through the breathing pores of the leaf 

 branching threads, and on these develops the conidia, as 

 already described. 



By means of these conidia, which are produced in 

 great abundance, and the swarm-spores originating from 



