446 



Journal of Agricultural Research 



Vol. X, No. 9 



Pticcinia graminis tritici, P. graminis tritici compacti, and P. graminis 

 secalis were found on Elymus canadensis (Table XIV). The grass is 

 attacked with approximately equal ease by all three forms. In 191 5 

 the wheat and rye forms were commonly found in the upper Mississippi 

 Valley, but in 1916, a year in which there was a very severe wheat-rust 

 epidemic, only P. graminis tritici was found, except in No. 4. A con- 

 siderable amount of rye is grown in the region from which this particular 

 grass material was obtained. It is interesting to note that both forms 

 of rust were present on the rye infected in this experiment. The rust 

 which developed in No. 4 was used in inoculating rye and wheat. On 

 the rye 15 out of 18 leaves became infected and 7 out of 43 wheat leaves 

 developed uredinia. 



Elymus canadensis is probably not as important as some of the other 

 grasses in stem-rust epidemiology. It may become very heavily rusted 

 but the rust often develops late in the season, and the grass may almost 

 entirely escape. The habit of growth may account for this fact. 



Diagram 5.— Results of inoculations with rust from -wheat and rye recorded in No. i, Table XIV. 



Puccinia graminis from Elymus canadensis. 



Wheat ^- 

 31 



Rye f-i 



o Very weak infection. 



Wheat I^ 

 IS 



Elymus canadensis — 

 Ryeb — 



Wheat - 

 45 



Elymus canadensis — 



12 



b Normal infection. 



Diagram 5 shows very clearly that both P. graminis tritici and P. 

 graminis secalis were present on E. canadensis in No. i. It should be 

 remembered, of course, that P. graminis tritici can infect rye weakly 

 while P. graminis secalis can not infect wheat. 



Table XV. — Results of inoculations with uredinios pores from Elymus condensatus 



Presl. 



No. 



Place. 



Date. 



Triiicum 

 vulgare. 



Avena 

 sati'va. 



Secale 

 cereale. 



Ritzville, Wash . . 

 EUensburg, Wash. 

 Pullman, Wash . . , 



1916 

 Oct. 3 



...do 



Oct. 5 



15. 



18 



; 3 



17 



16 

 o 

 18 



r4=7 



o 

 20 



