312 



GENERAL MORPHOLOGY OF PLANTS 



time up to the production of the cluster-cup again the cells of the mycelium 

 remain uninucleate. 



Upon the upper side of the spot are much smaller, yellow, conical elevations, 



Fig. 265. 



Wheat leaf with red 

 rust. Natural size. 



Figs. 265-266. 

 Figs. 267-269. 



& 



Fig. 266. Fig. 267. Fig. 268. 



Portion of leaf en- Natural Enlarged, 



larged to show sori. size. 



Puccinia graminis, red -rust stage (uredo stage) . 

 Black rust of wheat, showing sori of teleutospores. 



\ 



Fig. 269. 

 Single 

 sorus. 



Fig. 270. 



Uredospores of wheat rust, 

 one showing remnant of the 

 pedicel. 



Fig. 271. 



Germinating uredospore of 

 wheat rust. (After Marshall - 

 Ward.) 



Fig. 272. 



Germ tube entering the 

 leaf through a stoma. 



seen in cross section at fig. 263. These are the spermogonia. They produce 

 numerous very tiny, rod-shaped structures which ooze out at the opening of 

 the flask-shaped spermogonia in a gelatinous mass, sweetish to the taste. 

 Their function is not understood. 



