Vegetable and Field Crops 



235 



Black-heart.-^^' -'•'" — The centers of the tubers turn black 

 or become hollow with a black lining. This is due to ab- 

 normal physical conditions, such as high temperature, or 

 deficiency of oxygen, and occurs mainly in potatoes stored in 

 artificially heated rooms, or piled too deep (over 6 ft.). 

 Temperatures above 35° C. (95° F.) should be avoided, and 

 ventilation provided. 



Fig. 131. — Black-heart of potato caused by exclusion of air. After 

 Stewart and Mix. 



Spindling-sprout, the cause of which is unknown, is a 

 diseased condition in which the normal stout thick sprouts 

 fail to develop and in their stead are slender abnormally long 

 sprouts. Seed potatoes affected with this disease result in an 

 uneven stand with many missing hills, weak plants, and cor- 

 responding decrease in yield. 



Hollow-heart. — In years of abundant rainfall large pota- 



