FUNGI: THE SMUT FUNGI 



277 



Fig. 239. 



Corn smut (Ustilago zeae), 

 affected er, stalk, and blades. 



down between the young blades at the end of a growing corn stalk 

 they germinate, producing a germ tube which enters the tissues of 

 the corn plant and about six or eight 

 weeks later produces the smut masses 

 again. The infection is local in the 

 case of the corn smut, any of the em- 

 bryonic tissues of the corn being sus- 

 ceptible if the germinating sporidia are 

 present. The infection which produces 

 the smut at the lower joints of the 

 stalk takes place earlier than that in 

 the ear or that on the tassel. The corn 

 smut is often relished by cattle, and 

 does not seem to injure them unless 

 they eat too great a quantity. 



443. Other species of smut. 

 Other examples of smut are the 

 loose smuts on the grains, as the loose smut of oats (U. avence), 

 the loose smut of wheat (U. tritici), and the loose smut of barley 

 (U. hordei). The only part of the host injured is the flower, the 

 young kernels (ovary) and parts of the palets being reduced to a 

 black smutty mass con- 

 sisting of disintegrated 

 parts of the flower, the 

 mycelium, and the 

 spores. They are called 

 loose smuts because the 

 mass of spores not being 

 covered, even by any Fig. 24 o. 



rlpliVatA m^mhrariA tliA Corn smut, spore germinating and producing sporidia. 

 delicate memDrane, tne At t h e r i g ht. sporidia budding and producing secondary 



spores are easily scat- sporidia ' (Afte 



tered. Although only the flower parts are injured, the mycelium 

 travels all through the host while it is growing, from the seedling up 

 to the full-grown plant. The method of infection is very interesting. 

 In the case of the oat plant the smut spores clinging to the seed oats 

 germinate at the same time that the oat grains do. The sporidia 



