RUSTS 



28l 



the work of reproduction in spring, whence they are called 

 " winter spores," in contradistinction to the uredos or 

 "summer spores," whose activity seems to be confined to 

 the warm months. 



539. Uredospores of wheat rust, Puccinia graminis t magnified (from 

 COULTER'S " Plant Structures"). 



Under the microscope the teleutospores appear as long, 

 two-celled bodies with very thick black walls (Fig. 540). 

 Since they are developed from the same mycelium with the 



540. Teleutospores of wheat rust, magnified (from COULTER'S 

 " Plant Structures "). 



uredospores, and are not a product of the latter, but collat- 

 eral with them, the two constitute a single generation, and 

 belong to one and the same stage in the life history of the 

 plant. 



402. Sporidia, In spring the teleutospores begin to 

 germinate, each cell producing a small filament, from 

 which arise in turn several small branches. Upon the tip 



