220 PRACTICAL BOTANY 



210. Grape mildew : vegetative structures and nutrition. 



The downy patches that appear upon the leaves are merely 

 the superficial parts of the parasite, since within the leaf the 



Fig .180. A leaf of the grape, upon whioli may be seen the white, fluffy patches 



of grape mildew 



Photograph by H. H. Whetzel 



mycelial liyphse have grown for some time before the downy 

 patches are produced. These coenocytic hyphte grow between 

 the cells and send into the interior of the cells short branches 



