332 TEXT-BOOK OF FUNGI 



gives origin to the next cycle of development, which is 

 usually the uredospore condition. 



Uredospores may be produced from mycelium produced 

 from aecidiospores ; this is the usual mode by which 

 uredospores are first produced in the spring. During the 

 summer one crop of uredospores follows another in quick 

 succession without the intervention of any other form of 



FIG. 95. Hemileia vastatrix, a parasite causing the well- 

 known coffee leaf disease, i, portion of a coffee leaf showing 

 diseased patches ; 2, portion of a leaf showing a group of 

 sori ; 3, uredospores. Figs, i and 2, nat. size ; fig. 3, highly 

 mag. 



spore. Uredospores may also be produced by the 

 mycelium originating from the germination of promycelium 

 spores or secondary spores. In many instances uredo- 

 spores germinate at the moment of maturity, and only 

 retain their vitality for a short period of time. In some 

 species, however, as Puccinia graminis^ P. rubigo-vera^ etc., 

 the uredospores retain their vitality through the winter, and 

 are capable of infecting a proper host-plant the following 

 season. Uredospores are one-celled, have from two to 



