PARASITIC FUXGI 



9 



threads that run between the cells send into the cells 

 themselyes 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. ^Yhen they have 



FIG. 6. SUKFACE OF POTATO LEAF GHEATLY MAGNIFIED, SHOWING 

 GERMIXATIXG SPOKE EXTERIXG BREATHING PORE AT (/, 

 AND GOING THROUGH EPIDER3IIS AT C. 



developed to a considerable extent they collectiTely form 

 the mycelium of the fungus. 



After the Peronospora plant has reached this stage- 

 in its existence it is ready to ^Drepare 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 



