GRASSES OF IOWA. 243 



the neighboring states. This fungus converts the ovaries into 

 a powdery mass, consisting of spherical to ovoid spiny spores, 

 9-16 X 7-lP. 



Covered smut of switch grass {Ustilago syntherismfe. (Schw.) 

 Ell. & Ev.) This is widely distributed in the United States 

 and is indeed common wherever Panicum capillare, P. proliferum 

 Genclirus tribuloides occur. Norton,* who has studied the ger- 

 mination of Kansas smuts, places under this species provis- 

 ionally several of the smuts which are much alike. It certainly 

 appears that the forms on the above weeds germinate in much 

 the same way, but rather difficult in water. On Panicum iwoli- 

 ferum and Cenchrus tribuloides the ovaries as well as the whole 

 inflorescence become greatly enlarged, and for considerable 

 time the spore mass is surrounded by a white membrane, which, 

 on drying, breaks, allowing the spores to be liberated. The 

 spiny spores are variable in size, 10-12" in diameter, ovate or 

 somewhat polyhedral 12 x 14", to oblong polyhedral 12-14 x 

 8-10". This smut prevents the production of seed. The plants 

 are much dwarfed. The allied U. rabenhorstiana, Kuehnf, also 

 cjnvers the whole in florescence into a powdery mass. The 

 affected jDlants are dwarfed and more branched; the minutely 

 roughened spores are spherical to oblong elliptical 8-14 x 

 7-11.5". The promyceLum is branched; CDnidia are absent. 

 Another form affects the individual flower, and not the inflo- 

 rescense, as in the usual form. This smut is extremely common 

 and destroys a large number of plants every year in this state. 



Some of our cultivated grasses are aft'ected with other mem- 

 bers of the genus Ustilago. In some cases they affect very 

 valuable grasses. One of these, Ustilago bromivora var. macro- 

 spora, was found on one of oar native and valuable grasses, 

 Bromus breviaristatus, by Mr. F. A. Sirrine on the college farm. 

 This, as well as the smut on tall meadow oat grass, was 

 described by the writert some years ago. 



Brome grass smut affects parts of the flowers causing them 

 to develop into a powdery mass. In tall meadow oat grass I 

 also observed that all the stalks of a stool are affected, clearly 

 showing, that the Euogus enters early in the development 

 of the plant. The Ustilago bromivora, Fisch. de Wald. is 

 ai^parently the variety macrospora of Farlow. It occurs- abun- 



*The Kansas Ustilaginleae. Trans. Acad, of Sci. St. Louis. 7: 235. 

 +Hedwigia. 15: 4. 1876. 

 Saccardo Syll. Fung. 7: 471. 

 tjour. Myc. 7: 98. 



