202 



Diseases of Econornic Plants 



vive until harvest. The disease is more? often fatal if attended 

 by dry weather, which reduces the vigor of the host plant. 



Fig. 107. — Young onion plants showing effect of smut. 

 At left, smutted plants; at right, healthy plants of 

 the same age. After Hinman, 



Plants surviving the disease show smut in the outer leaves, 

 often also within. Diseased bulbs dry up and rot. In han- 

 dling they may readily be distinguished from sound bulbs. 

 The spores are liberated freely in the soil, where they 



