Vegetable and Field Crops 



227 



the tubers begin to form. The coalescence of the spots 

 involves large areas of leaf tissue and results in browned, 

 withered leaves, the stems remaining green. The illusion 



125. — ■ Potato attacked by Corticium. 

 After Rolfs. 



is often so complete as to lead the grower to think that the 

 vines have died a natural death. The progress of the disease 

 is slow, three or four weeks intervening before all the leaves 

 are dead. The loss of efficient leaf tissue so diminishes the 

 vigor of the plant that the yield is largely reduced. Early- 



