3 i8 TEXT-BOOK OF FUNGI 



swellings that may attain to the size of an apple, and 

 occur either on the stem, leaves, or fruit. 



In some instances infection of the host-plant is only 

 possible during a very short period after germination ; the 



FIG. ^. Urocystis celchici. i, portion of a leaf of Col- 

 chicum autumnale with numerous sori of teleutospores ; 2, a 

 single sorus bursting through the epidermis of the leaf ; 3, 

 spores, showing the central living cells surrounded by empty 

 sterile ones. Fig. i, nat. size ; fig. 2, slightly mag. ; fig. 3, 

 highly mag. 



mycelium of the fungus grows along with the host without 

 doing any apparent injury until the spores are formed in 

 the ovary or on the leaves. In the case of maize, however, 

 infection can occur at any period of growth provided quite 

 young tissue is present. 



