Aug. 27. 1917 Puccinia graminis on Cereals and Grasses 



453 



rye, and the three species of Hlymus became infected, while only a small 

 percentage of the wheat leaves developed uredinia. Barley and the three 

 grasses v^rere known to be congenial hosts for both forms of the stemrust. 

 It was therefore to be expected that each was infected with the two. This 

 proved to be the case, but evidently more of the rye form was present 

 than of the wheat form, as would also be supposed from the results in 

 No. 3. This is shown in the diagram by the fact that not all of the inocu- 

 lated wheat leaves rusted, while all of the rye leaves did. The weak 

 infection which resulted on Agropyron repens and rye from the inocula- 

 tion with the rust developed on wheat showed that the wheat developed 

 only the wheat form, while the rye very clearly developed only the rye 

 form. 



Diagram 8. — Results of inoculations •with urediniospores developed on Elymus canadensis and Secale 



cereale in No. 3, Table XX. 



Hordeum jubatum — — Wheat 

 20 



08 



Puccinia graminis from 

 Hordeum. jubatum. 



. 81 

 Elymus canadensis j" — . 



A gropyron repens 



Wheat 



55 



Barley 



Rye~ — 



Rye-'iL 

 24 



Rye: 



[Agropyron repens 



Hordeum jubatum — 



Wheat 



\Agropyron repens -^ 



o Very weak infection. 



Barley — 

 24 



12 

 Rye — — 

 34 



Wheat — 

 I 44 



* Minute uredininm. 



Wheat 



L 26 



iRye::z 



<^ Very heavy infection. 



In 1 91 6 very little of the secalis form developed. The rust developed 

 on rye in No. 31 was of this form. Except for this one lot of material, 

 however, little or none of the secalis form was found during the summer. 

 The uredinia developed on rye in the other trials were small and the flecks 

 sharp, indicating the presence of P. graminis tritici. Inoculations from 

 rye to wheat and rye also showed this to be true. P. graminis tritici 

 compacti was found on Hordeum jubatum only at Pullman, Wash., west 

 of the Rocky Mountains. The rusts east of the mountains were practi- 

 cally the same, although there sometimes appeared to be slight differences 

 in virulence. 



