94 



THE FUNGI WHICH CAUSE PLANT DISEASE 



the fungus in that conidia are produced more abundantly and 

 retain their power of germination longer when moist. Disease 

 spots appear two or three days after infection; conidia same nine 

 or ten days after infection. 



The species is perennial in Florida '' and spreads northward as 

 the season advances, reaching Ohio and New York by late summer 



Fig. 64. — P. cubensis: 3. Conidiophore with young and 

 old conidia. 5. Conidium. 6. Conidium germinating. 

 11. Zoospores. 18. Infection through a stoma. 

 After Clinton. 



or early autumn.** For a series of years after its discovery it was 

 not well known even scientifically, its first serious outbreak being 

 about ISS9.^ It appeared in Japan about the same time ^ and 

 is now known to be almost cosmopolitan. The oospores have 

 been found only by Rostewzew and have not been seen in America. 

 A wide range of wild and cultivated cucurbits is infected, among 



