240 GRASSES OF IOWA. 



was 1.6 per cent. On this basis Swingle* estimates the loss in 

 that state to be $26,454. From these figures Swinglef thinks 8 

 per cent a low average. This would entail a loss of $18,000,000 

 annually. Averaging 18,504,140 for the years 1890-1893. 



Oq our own grounds we have found oats smut less common 

 than the figure given by Swingle. X Harwood and Holden§ esti- 

 mated the loss in Michigan in 1892 at $1,000,000. 



Is it any wonder that smut should be so abundant since a 

 single head may contain millions of spores? 



Dr. Cobb says: "A single head of smutted oats may easily 

 contain 500,000,000 spores; that is to say, a number of spores 

 so great that if they were distributed evenly over an acre of 

 land there would be over 1,000 spores on every square foot. 

 In as much as these spores are instrumental in spreading the 

 smut disease, we shall no longer wonder at finding the disease 

 so common. " 



KERNEL SMUT OF OATS. 



In addition to the above smut {Ustilago avence (Pers.) var. 

 levis, Kellerman and Swingle) another form has been observed 

 by Kellerman and Swingle,! which destroys only the grain and 

 does not affect the glumes. On cutting open such a diseased 

 husk the who'e interior of the grain will be found converted 

 into a powdery mass consisting of spores. This spesies was 

 collected by Farlow and distributed by Ellis*" in his North 

 American fungi. The spores of this smut are dark brownish, 

 oval, elliptical or subglobular, 6-12 x 55-8", usually 6-9x6-7". 

 The exospore is nearly smooth. The spores germinate readily 

 in nutrient solutions, producing short promycelia and narrow 

 germ tubes. The species is probably quite widely distributed 

 though not nearly so common as Ustilago aveme. 



BARLEY SMUT. 



Barley is affected by two well-known smuts in Iowa. The 

 covered barley smut {Ustilago hordei (Persoon) Kellerman and 

 Swingle) and the naked barley smut {Ustilago nuda (Jensen) 

 Kellerman and Swingle). Formerly both of these smuts were 



♦The Grain Smuts. Their Causes and Prevention. Year book U. S. Dept. Agr. 

 1894: 413 



tl.c.413. 



*Bull. Mich. Agrl. Exp. Sta. 87: 189. 



§Rep. Kansas Agrl. Exp. Sta. 6: 259. 1893. 



llEllls. North Am. Fung. 1091. 



"^Swlngle. Year Book U. S. Dept. Agr. 1894: 412. Farmers' Bulletin U. P. Dept. 

 Agr. 75. 



