DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 515 



The oogonia and antheridia are not so common as the conidiospores. 

 If the shriveled parts of the leaves are examined in September, the 



Fig. 186. — Grape leaf attacked by mildew, Plasnwpara vilicola, Cold Spring Harbor, 

 L. I., Aug. 2, 1915. 



oogonia will be found as spheric organs attached to the intercellular 

 hyphae by a short stalk. One or several filamentous curved antheridia 

 are formed near the oogonia to the surface of which they become ap- 



