400 



DISEASES OF CULTIVATED PLANTS 



Most closely allied to Hypochnus, differing in being parasitic, 

 with immersed mycelium, and in the basidia bearing a variable 

 number of spores. 



Rhododendron galls (Exobasidium rhododendri, Cram.) 

 form on the living leaves of Rhododendron hirsutum, R. fer- 

 rugineum, R. Wilsonianum, etc., and vary in size from 



FIG. 125. Exobasidium rhododendri, on leaves of rhododendron, 

 slightly reduced ; 2, basidia and spores of same, highly mag ; 3, 

 Hypochnus solani on lower part of a potato haulm, slightly 

 reduced ; 4, mycelium and basidia of Hypochnus, highly mag. 



a pea to that of a cherry. These are at first pale green, at 

 length often becoming red or brownish. When full grown 

 the surface is covered with a delicate whitish bloom, due to the 

 presence of innumerable minute conidia, produced by budding 

 in a yeast-like fashion from the basidiospores. The mycelium 

 is very abundant between the cells at the periphery of the 

 gall, but . scanty elsewhere. Small globose haustoria are 

 present in the cells of the host. 



Basidia covering the surface of the galls, clavate, sterigmata 



