GRASSES OF IOWA. 187 



orders of flowering plants are affected by downy mildews, few 

 of these pests are found on grasses. This fungus, though well- 

 known for some years in Germany and Italy, has not been long 

 known in this country. It was first reported in Wisconsin, as 

 occurring on Hungarian grass {Setaria italica) and foxtail and 

 pigeon grass {Setaria viridis). Dr. Halsted* reported it from 

 Iowa on the last named host in 1886, and the next year on 

 Hungarian grass. 



It is now common throughout the state of Iowa. The fun- 

 gus has been found by the writer quite as common in Nebraska 

 as in Iowa. Webber f gives its distribution in that state, 

 Ashland, Weeping Water (Williams), Lincoln (Bessey), where 

 he found it on green and yellow foxtail {Setaria viridity S. glauca). 

 have also received it from North Dakota, where it was collected 

 by Prof. Bolley. Like many other pests, it comes from Europe, 

 and in all probability was brought to this country with the seed 

 of either Hungarian or foxtail, as both grasses are native to that 

 continent. 



Little mention is made of this fungus by Tubeuf, t and it is 

 not mentioned by Loverdo. § The account by Sorauer is short, 

 A good account was given by Trelease;|| it was also described 

 by Farlow.l 



Halsted,** who found it common here at Ames, reported on 

 it in several publications. 



The fungus produces a mycelium in the interior of the leaves 

 and soon sends short branches conidiophores through the sto- 

 mata. These bear the conidia, the summer reproductive bod- 

 ies. Last spring I had an opportunity of observing an unusually 

 large number of young diseased plants. A white frosty-like 

 substance' (the conidia and conidiophores) appeared on the leaf 

 in patches extending along the veins. The opposite side of the 

 leaf was invariably of a yelloA-ish color. In July and August 

 the summer spores are not so commonly seen, especially in the 

 older leaves. Last spring the weather was quite favorable for 

 the deve'opment of this fungus. Young plants affected soon 



♦Trelease. Parasltlo fungi of Wis. 7. 



*Bot. Gaz. 11: 272. 



+App. to Oat. PI. Nebr. Oontr. Shaw School Bot. 9: 11. Trans. Acad. Sci. St. 

 Louis. 6. 



tPflanzenkrankhelten. 153. 



SLesmaladles des cereales. 



Illn Seal. Grasses of No. Am. 1: 439. 



HBot. Gat. 9: 39. 



♦*Bot. Gaz. 11: 372. 13: 58. Bull. Iowa Agrl. OoU. Dept. Bot. 1886: 53. Bull. 

 Dept. Bot. Iowa Agrl. Ooll. 1888: 99. 



