juneio, i9i8 Experiments with Coccomyces spp. from Stone Fruits 569 



The variations of results in difficult crosses with conditions not yet 

 fully understood make it unwise to place too strong reliance upon 

 negative results. 



It is apparent from these tests, though not fully conclusive, that in 

 Wisconsin no serious infection of cultivated cherries is induced by inocula 

 from wild hosts, with the possible exception of P. pennsylvanica. It is 

 evident, however, that the native P. americana may act as a harborer of 

 infectious material for cultivated plums. 



This work has defined rather than solved, certain fundamental prob- 

 lems regarding host relationships and specialization of parasitism within 

 the group of fungi under investigation. 



