Minnesota Plant Diseases. 



thick and hard. These 

 spores are produced in 

 enormous numbers re- 

 placing all of the 

 grains and are then 

 seen as a smutty pow- 

 der which is familiar to 

 every farmer who 

 raises oats. These 

 smut-spores are now 

 in an advantageous 

 position and are scat- 

 tered by the wind and 

 carried to sound grains 

 and may, as described 

 above, again cause 

 infection of the oat 

 in the seedling stage 

 in the following 

 spring. This life-story 

 explains the success of 

 the hot water method 

 in preventing oat 

 smut, for if the smut 

 spores, clinging to the 

 grains are killed by 

 steeping in hot water, 

 which will not injure 

 the grain, then the 

 chances of infection of 

 the seedling plants 

 from these treated 

 grains are greatly re- 

 duced or entirely de- 

 stroyed. 



157 



Fie. 72. Loose smut of wheat. 

 (Ustilago tritici. ) The loose 

 powder of spores has been par- 

 tially shaken out; the grains 

 of the wheat are all smutted. 

 Original. 



