242 GRASSES OP IOWA. 



Ustilago hordei, is found in the fact that the spores are free, 

 and do not adhere to each other or to the shreds of the host 

 tissue. The infecting threads, unlil^e those of the Cstilago 

 hordei, grow to their normal height, and do not tend to remain 

 enclosed by the uppermost sheath of the barley plant. " In 

 Ustilago hordei the thin membrane encloses the smutted kernel 

 until harvest time. The spores are free, forming a dark mass 

 of olive color, sometimes elliptical or sub-globose, usually the 

 one side lighter than the rest, as in the other loose smut. The 

 spore wall consists of two parts, the exospore and endospore. 

 The exospore of U. nuda is slightly roughened. The spores 

 germinate in sterilized water and nutrient sugar solution under 

 favorable conditions of temperature usually in twenty-four 

 hours or less. The promycelium or germ tube comes out of a 

 large germ pore. It is curved and slender. According to Kel- 

 lerman and Swingle it attains its full length in thirty hours. 

 Sporidia are not produced, according to Kellerman and Swin- 

 gle. This smut occurs in Kansas, Iowa, Wisconsin, New York, 

 Michigan, Minnesota and Europe. 



Manner of infection. — Little is known of the mancer of infec- 

 tion; the seeds of the smut apparently propagate the smut so 

 that infection is carried with seed barley. 



WILD BARLEY SMUT. 



This smut {Ustilago lorentziana), converts the ovary, palet 

 and flowering glume of Hordeum Jubat um into a black, powdery 

 mass, a? in Ustilago nuda. The spherical spores are minutely 

 roughened. This species does good service in the northwest 

 in destroying much of this detestable weed. 



OTHER SMUTS OF THE GENUS USTILAGO. 



Pigeon-grass smut {Ustilago neglecta, Niessl.) The most 

 common of our smuts is that occurring on Setaria or pigeon- 

 grass (-S'. glauca.) Ustilago neglecta. was first described by Niessl* 

 and has been reported by numerous American and European! 

 mycologists. In Europet it is said to effect S. glauca, S. verti- 

 cillata and S. viridis. I find, however, no record of its occur- 

 rence on any other host but S. glauca in this country. § On this 

 host|| it is extremely common, not only in Iowa, but throughout 



*Rabenhorst, Fung. Europ. 12(X). 

 +Wlnter die Pilze. 1 : 97 as IT. Panicici-glauct. 

 tTubeuf. Pllanzgnkrankhelten. 306. 

 §Saccardo, Syll. Fung-. 7: 472. 

 II Farlow and Seymour. Host Index. 



