FUNGI, THE SMUT FUNGI 



307 



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

 formed on the promycelium germinate and the germ tube enters 

 the oat seedling at the base of the first leaf sheath. In the case of 

 the loose smut of wheat and barley the method of infection is 

 different. At the time the wheat or barley is in flower, the smut 

 on the affected plants in the field is just ripening, and spores are 



Fig. 255- 



Loose smut of barley (Ustilago 

 nuda.) J diameter. 



Fig. 256. 



Bunt or stinking smut of wheat 

 (Tilletia tritici). Note the flaring 

 position of the palets. 



blown from the smutted heads to the open flowers of healthy 

 plants. The spores lodge on the feathery style of the flower and 

 germinate. They do not produce a promycelium, but the germ 

 tube of the spore enters directly into the style, and passes down 

 into the ovary, where it forms a small amount of dormant myce- 

 lium which, however, does not injure the grain, so that it ripens 

 with the dormant mycelium of the smut imprisoned. When 

 these grains of wheat are sown, the dormant mycelium begins to 

 grow as the seed germinates, and passes through the scutellum 



