PLATE 22 



A. — Blackrot of sweet-potato slips caused by Sphaeronema fimbriatum. Note the 

 black cankers on the underground part of the stem. The causal fungus grew onto the 

 slips from a blackrotted potato used for seed. The use of infested soil in the hotbed will 

 cause similar infection. 



B. — Blackrot on a bedded sweet potato. Note the yotmg sprouts not yet through 

 the grovmd being invaded by the fungus. 



