232 



Diseases of Economic Plants 



browned or blackened from near the surface of the soil down- 

 ward. In extreme cases the discoloration was visible 2-3 cm. 

 above the soil. The tissues of the discolored part died, and 



the softer parts decayed. Usually the seed tuber also was 

 rotted. Loss as high as 20 per cent is reported in Maine, 

 75 per cent in certain fields in Michigan ; but such large loss 

 is unusual. 



The disease is carried over to succ(HM:ling crops in the seed, 



