CEREALS 365 



TEOSINTE 



Smut. See com. 

 Rust. See com. 



WHEAT 



Black stem rust (Puccinia graminis Pers.). — Though in 

 eariier years this rust was thought to grow indiscriminately 

 upon a great variety of grasses, recent thorough study 

 has shown that what was formerly regarded as one species 

 is in reality a number of races or varieties grouped under 

 one name. The variety now under discussion is known to 

 grow upon barley and wheat and upon several species of 

 Elymus and Agropyrum and other genera of wild grasses. 



It is one of the most serious of the rusts, though fortunately 

 not so universally present as the orange leaf rust, and causes 

 more damage in the Central States than any other rust 

 except the oat black stem rust. The damage done fluctuates 

 largely. In some years it is very large, in others compara- 

 tively slight. In 1904, a year of especially severe attack, 

 the direct loss in yield was placed at 30,000,000 bushels in 

 the Northwestern States, in addition to the loss in grade 

 of the grain that was harvested. Total loss of the crop 

 often results in Kentucky, Indiana, Texas, Michigan, and 

 Ohio. 



Its spring or cluster-cup stage is upon the barberry, 

 where swollen spots are produced upon the leaves, fruit, or 

 young stems. These spots upon one side bear the cups in 

 abundance and upon the other side appear as pale circular 

 regions. 



Upon the wheat the rust shows first its uredosori, which 

 come later than the uredosori of the orange leaf rust, and 



