454 



Journal of Agricultural Research 



Vol. X, No. 9 



Probably no grass is responsible for spreading more wheat stemrust 

 than Hordeum juhatum. It rusts early in the season, especially near bar- 

 berries, and during a season favorable to rust development it becomes 

 almost universally rusted. In amount of rust developed it is approached 

 probably only by Agropyron repens, which, however, is host for P. graminis 

 secalis, not P. graminis tritici. Inconceivably large numbers of uredini- 

 ospores are developed by these grasses, and when the rusted grass is dis- 

 turbed on windy days clouds of spores, which are probably carried con- 

 siderable distances by the wind, can easily be seen. 



Diagram 9. — Results of inoculations with urediniospores from Hordeum, fiusillum Nutt. 



Wheat ;^ 



Urediniospores from Hordetim pusillum 



Oats 



29 



The rust was collected in the grass garden on University Farm, St. 

 Paul, Minn., and inoculations were made on August 30, 1916. Both the 

 wheat and rye forms were present (see diagram 9). 



Table XXI. — Results of inoculations with urediniospores from Hordeum vulgare 



No. 



Place. 



St. Paul, Minn 



Ramsey Co., Minn. 

 do 



Hinckley, Minn. a 



Pine City, Minn.o 



Emerson, Manitoba , 



Portage la Prairie, Manitoba*. 

 Williston, N. Dak 



1915- 

 July 17 



..do 



Oct. 14 

 1916. 



Triticum 

 vulgare. 



£2 

 31 



Avena 

 sativa. 



o 

 16 



23 



Hordeum 

 vulgare. 



14 



IS 



Secale 

 cereale. 



o 



12 



I 

 29 



15 



10 -^ 

 2 



15' 4 



2 

 19 



15. J 



o Greenhouse conditions unfavorable for infection. 

 & Hooded barley. 



