236 



GRASSES OF IOWA. 



germinating plant becomes older 

 and its tissues harder of pene- 

 tration by the threads, infection 

 becomes less possible until, at 

 the time when the plant breaks 

 through the ground and its first 

 leaves show, it is practically 

 exempt from successful infec- 

 tion. " Short treatment of the 

 seed with warm water has no 

 injurious effect. Experiments 

 made for three years by Clinton 

 showed favorable results by 

 treating with hot water. The 

 sports were killed at 135"^ F, 



Ustilago cruenta. — Another 

 smut affecting this host has been 

 described by Kuhn* — the Usti- 

 lago cruenta. This species pro- 

 duces brownish-red spherical or 

 elongated enla-gements which contain the smut spores affect- 

 ing any part of the panicle. The somewhat variable spores 

 are 5-12" long x 5-9" wide, smooth yellowish or brownish, 

 germinate readily in water, and in riutrient solutions produce 

 abundant secondary conidia. Kuehnf surmises that it is the 

 cause of a destructive disease Durra of millet in Africa. 



tig. 115A. Kernel smut of sorg-hum 

 (Ubtilago sorghi) . The affected inflor- 

 escence to the right and spores to the 

 left. 



LOOSE SMUT OF WHEAT. 



For a long time all of the loose smuts — oats, wheat and 

 barley {Ustilago tritici (Persoon) Jensen) — were considered by 

 botanists to be one species, to which the name Ustilago segetum 

 (Bull ) Dittm.J was applied. This smut was known to writers 

 as early as 1552, when Tragus§ applied the name Ustilago 

 An early writer, Bauhin, 1595, described it as Ustilago secalina. \\ 

 None of the early writers, however, recognized it as a fungus. 

 Persoon, an early mycologist, gave it the name of Uredo tritici,^ 

 considering it a variety of Uredo segetum. Other names were 

 subsequently applied, and in 1888, Jensen** reported that wheat 



♦Hamburger Garten u. Blumen Zeltig, 28: 177. 



+Tubeuf. Pflanzenkrankheiten. 305. 



$Sturm Deutsch. Fl. 3: 67. pi. 33. 



SDle Stlrplum Nomencl. Prop. Lib. 3: 669. 



IIPhytoplnax.52. 



i;3yn. Math. Fung. 224. 



**The Prop, and Prev. of Smut in Oats and Uarley. Jour. Roy. Agrl. Soc. 24: 9. 



