PLATE 24 



A. — An originally healthy sweet potato sprayed with the spores of Sphaeronema 

 fimbriatum and confined in a moist chamber. The infections take place mostly 

 through small rootlets or through wounds. 



B. — A typical blackrot spot on a sweet potato as usually foimd at digging time or in 

 storage. 



C. — Cross sections of blackrot sweet potatoes, showing the depth to which the fungus 

 will sometimes penetrate. Pvue cultures of Sphaeronema fimbriatum were obtained 

 from the deepest portion of the rot of these two sections. 



