LOOSE SMUT OF OATS 



211 



Swingle estimates the annual loss at not less than 

 $18,000,000 for the United States alone. 



The smut or mass of spores is produced in the ovary, 



*> 



Fig. 50. Ustilago avenae. i, a 'smutted' ear of oats; 

 2, spores, X30o; 3, germinating spores, XSOQ; 4, secondary 

 spores conjugating, x 300. 



and matures when the oat is in flower, and is dispersed 

 by wind or rain before harvest. 



A form of this species called laevis, on account of the 

 smooth spores, has been recorded from America, growing 



