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BOTANY: PRINCIPLES AND PROBLEMS 



ratus. Whatever its original share in the Hfe cycle may have 

 been, however, it seems now to be entirely functionless. On the 

 lower surface of the barberry leaves are formed cluster-cups or 



Fig. 174. — Puccinia graminis, the wheat rust. A, wheat leaf with groups of 

 summer spores (uredospores). B, uredospores (one teleutospore among them). 

 C, germinating uredospore. D, wheat stem with masses of winter spores (tel- 

 eutospores). E, two teleutospores. F, germinating teleutospore, producing a 

 promycelium on which are borne the sporidia. G, sporidium germinating on 

 epidermis of barberry leaf. H, lower surface of barberry leaf, showing cluster- 

 cups or aecidia. /, section through the leaf of barberry showing spermagonium 

 on upper surface and aecidium on lower. The aecidium is producing masses of 

 aecidiospores, which infect wheat plants. {B, C, F and G after De Bary). 



aecidia (singular, aecidium), flaring, cup-shaped structures from 

 the base of which arise long rows of aecidiospores. These, in 



