j A. R 



Kanred | g ç;, 



[newton] wheat stem RUST 209 



Explanation of Plates 



PLATE I 



A Group of Differential Hosts Inoculated With: 



A. Form XVH. 



B. Form XVHI. 

 Compare: 



Resistant. 



Susceptible. 



Arnautka \ , „ ., , 



,-. J I A. Susceptible. 



o 1^ HT (B. Resistant. 

 Speltz Marz i 



Other minor differences are not distinguished clearly in the photograph. 



PLATE II 



Leaves of Little Club 



A very susceptible variety, showing normal appearance and size of the uredinia 

 when inoculated with any one of the 14 biologic forms isolated. 



Leaves of Khapli (X2 1/2) 



The only variety resistant to all the forms isolated. 



a and h. Small uredinia on dead areas. 



c. Minute areas of killed leaf tissue, where no uredinia were formed. 



PLATE III 



Leaves of Three Grass Species Inoculated with Form XVII 



A. Bromus carinatus H and A — Resistant. Note chlorotic areas. 



B. Bromus villosus Forsk — Resistant. Note chlorotic areas. 



C. Agropyron tenerum Vasey — ^Very susceptible. Uredinia large and well 

 formed. 



PLATE IV 



Development of Puccinia Graminis Tritici within the Tissues of a Sus- 

 ceptible Host (Marquis Wheat) 



All the drawings in this and succeeding plates were made with a camera lucida. 



5. Transverse section of leaf showing the urediniospore germ tube with appres- 

 sorium, and the passage of the germ tube through the stoma. 



6. Longitudinal section of leaf showing an appressorium formed above a stoma. 



7. The formation of a swelling or appressorium at some distance from a stoma. 



8. The entry of the germ tube and the formation of the sub-stomatal vesicle. 



9. The infecting hyphae striking across the sub-stomatal space to branch 

 between the cells. 



14— E 



