238 FARM FRIENDS AND FARM FOES 



The Crown Rust or Orange Leaf Rust of oats is an 

 abundant and widespread disease. Technically it is known 

 as Puccinia coronata. It has a life history very simi- 

 lar to that of the Black Stem Rust, the spring spores or 

 aecidiospores being developed upon buckthorn instead of 

 barberry. There seems little doubt, however, that the 

 fungus can pass through the year in the absence of this 

 aecidium stage. 



Serious injury by the Rust of Indian Corn is only rarely 

 reported, although the fungus is very common. It appears 

 on the leaves in brownish pustules of uredospores that 

 develop during summer. They are followed later in the 

 season by blackish teleutospores which live over winter 

 to start the disease anew in spring. This fungus is known 

 as Puccinia Sorghi. 



CEDAR AND APPLE RUST 



Another good example of a heteroecious rust is the one 

 that causes the "cedar apples" so often found on cedar 

 trees. These are curious little orange-colored balls that 

 occur along the twigs. In autumn and winter they have 

 smooth, rounded surfaces, but in spring they send out curi- 

 ous jelly-like masses about half an inch long. The teleu- 

 tospores germinate by sending out tubes that give rise to 

 secondary spores or sporidia. These sporidia are blown 

 about by the wind : such as fall on moist leaves of apple, 

 quince, or June-berry are likely to germinate and start a 

 growth of mycelium within the leaf. 



This mycelium soon gives rise to swollen pustules called 

 cluster cups or aecidia. In these millions of brownish 

 aecidiospores are developed. These are blown about by 

 the wind, and such of them as chance to light upon moist 



