Fungi 



419 



barberry stage is of special importance in the life history of the 

 rust. In the southwestern United States, where winter wheat 



Fig. 260. The white-pine blister rust. The fruiting bodies on the white 

 pine {A) produce spores that infect the leaves of the gooseberry {B and C). On 

 the gooseberry leaves the fungus produces at first yellow spores that will infect 

 other gooseberry plants, and later brown spores that carry the disease back to 

 the pine. When a pine (D) is infected by the disease, the younger parts soon 

 die (£). 



is grown, the red spores produced during the summer may be 

 carried from one field to another by the winds and infect the wheat 

 over wide areas. In the Northern states the destruction of all 

 barberry plants has been undertaken, and this work has already 

 reduced the amount of infection. The hope of entirely control- 

 ling wheat rust, however, probably lies in breeding new varie- 

 ties that are immune to the disease. This has been accomplished 

 in Kansas producing a variety known as " Kanred wheat." 



Apple rust. Other rusts also live on two host plants, and be- 

 cause of this double life and the fact that the fungus grows on 

 the inside of its host, they are very difhcult to control. The rust 

 on the red cedar produces the so-called " cedar apples." In the 

 spring these swell and protrude masses of teliospores that germi- 

 nate at once and form basidiospores, which infect the leaves of the 

 apple tree and may do great damage to them. 



