248 



DISEASES OF ECONOMIC PLANTS 



very young state without infection, are so protected by 

 hardening of the outer plant parts that no infection is 



Fig. 111. — Young onion plants showing effect of smut : at left smutted plants, at 

 rigiit healthy plants same age. After Hinman. 



likely to result, even if the bulb be surrounded by thor- 

 oughly infested soil. 



