260 



THE FUNGI 



germination of the spores. The smuts of oats and wheat often 

 cause enormous loss in these crops. The best preventive measures 

 seem to be, treatment of the grains with solutions of copper sul- 

 phate, or formalin, or steeping them in hot water for a short time 

 before planting, which kills the smut 

 spores without injuring the grain. 1 



275. The rusts. The rusts (order 

 Uredinales) cause some of the most 



FIG. 229. The wheat 

 rust (Pucciniagram- 

 inis) 



A, spots of the red rust 

 on a wheat leaf, com- 

 posed of the summer 

 spores (uredospores) ; 

 B, spots of the hlack 

 rust on wheat straw, 

 composed of the 

 winter spores (teleuto- 

 spores) 



FIG. 230. The winter spores (teleuto- 

 spores) of the wheat rust (Puccinia 

 graminis) 



Section through a spot of the hlack rust on 

 oats, the epidermis of the leaf being 

 thrown back and the two-celled teleuto- 

 spores raised above the surface on stalks ; 

 note the web of fungal filaments (hyphae) 

 around the very much enlarged (hyper- 

 trophied) cells of the host under the spot 



disastrous diseases of such grains as wheat, oats, barley, and 

 rye. They are all parasites, forming yellow or black spots on 



1 See Swingle, "The Prevention of Stinking Smut of Wheat and Loose 

 Smut of Oats," United States Department of Agriculture, Farmer's Bulletin 

 250, 1906. 



