EXPLANATION OF PLATES 



The drawings were all made with the aid of the camera lucida. The Zeiss 

 3 mm. N. A. 1.3 homogeneous oil immersion and compensating ocular No. 4 

 were used for all except Figures 8 and 10, Plate IX, where compensating ocular 

 No. 6 was substituted. 



Plate I A. Rye after inoculation with Puccinia graminis hordei, showing dead 

 leaf areas and a very few minute pustules. 



B. Normal but rather light infection on rye by P. graminis secahs, showing 

 absence of dead areas. 



Plate II A. Einkorn 2433 inoculated with P. graminis originally obtained from 

 wheat and confined to Einkorn for twenty-five successive generations. 

 B. Einkorn 2433 inoculated with P. graminis from wheat. 



Plate III A. Wheat, Minnesota No. 163, inoculated with rust which had been 

 confined to Einkorn for twenty-five generations. 



B. Normal infection of wheat following inoculation with P. graminis tritici 

 from wheat. 



Plate IV A. Kubanka 1516 grown in very wet soil after inoculation with 

 P. graminis. 

 B. Kubanka grown in very dry soil after inoculation. 



Plate V A. lumillo 1736 grown in very wet soil after inoculation with P. 

 graminis tritici. 



B. The same variety inoculated under same condition but grown in very 

 dry soil. 



Plate VI A. Khapli, showing characteristic infection following heavy inoculation 

 with P. graminis. 

 B. Normal infection on Minnesota No. 163. 



Plate VII. Infection of Minnesota No. 163 wheat by P. graminis tritici. 

 1, 2 and 3 48 hours after inoculation. 

 4 and 5 72 hours after inoculation. 

 6 to 9 5 days after inoculation. 



1. Surface view showing appressorium forming over a stoma. 



2. Appressorium being formed directly, without germ tube development. 



3. Germ tube apparently passing over stoma and forming a swelling an 



unusual occurrence. 



4. Part of a germ tube, appressorium, and neck connecting the appressorium 

 with the substomatal vesicle which has been cut at one side. 



5. Substomatal vesicle, cut at one side, beginning to branch. 



6. Infection thread growing from vesicle directly across substomatal space; 



remains of appressorium outside. (Section slightly torn.) 



7. Part of an infection thread showing haustorium in epidermal cell. 

 8 and 9. Later stages showing development of long hyphae. 



Plate VIII. Infection of Khapli with P. graminis tritici. 

 1 and 2 72 hours after inoculation. 

 3 and A 6 days after inoculation. 

 5, 6 and 7 8 days after inoculation. 



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