434 



General Botany 



//. B. Humphrey, U.S.D.A. 



Fig. 270. Smuts of small grains: A, loose smut of wheat; B, loose smut of barley; 

 C, covered smut of barley. In each figure one of the heads is free from disease. 



smut of oats, wheat, and barley and the loose smut of oats may 

 be successfully prevented by treating the seed with formaldehyde 

 before planting. This is possible because the plant is carried 

 over the winter by spores on the grain or by masses of spores 

 (smut balls) among the grain. 



The loose smuts of wheat and barley cannot be successfully pre- 

 vented by formaldehyde treatment, because the fungus is carried 

 over from one year to the next by means of living hyphae inside 

 the grain. These fungus hyphas, however, cannot withstand a 

 temperature of 125° to 130° F., while the seeds of wheat and 

 barley are uninjured by a lo-minute exposure to this temperature. 

 Consequently a method of control has been devised by which the 

 grain is dipped for 10 minutes into water carefully maintained 

 at 129° F. Detailed directions for both the formaldehyde treat- 

 ment and the hot-water treatment may be obtained from your 

 State Agricultural Experiment Station. The hot-water treat- 



