PHVCOMYCETES 



155 



which may appear upon the shoots, as subsequently described. 

 Commonly the fungus is found upon the berries only when the 

 latter are young, although a form of brown rot, sometimes called 

 gray rot, may be produced by this fungus when the berry is more 



FIG. 53. PLASMOPARA ON GRAPE, (b and d after Farlow) 



a, mycelium ; , mature conidiophore ; c and d, zoospore and oospore 



formation, respectively 



than two-thirds grown (see illustration facing page i). Upon Vitis 

 cordifolia the fungus may fruit so abundantly upon the young berries 

 as to completely envelop them in a downy mass of sporophores. 

 Under such circumstances the berry does not at that stage show 

 evidences of decay, and it is only when the berries are older, and 

 in other species nearly full grown, that the fungus produces a 

 true decay. When the disease occurs upon the young fruits the 

 financial losses may be severe. 



