_; ;. ^A STUDY IN CEREAL RUSTS 



1. Part of a germ tube and an appressorium. 



2. Germ tube, appressorium, and substomatal vesicle into which the nuclei 

 have passed. 



3. Infection thread, with a few short branches, killing the host cell. The 

 protoplast has shrunk and the nucleus is disintegrating. 



4. Infection thread in contact with a cell which it is apparently killing. 



5. Substomatal vesicle and a number of somewhat abortive infection 

 threads. In the epidermal cell on the left two haustoria, deeply stained, 

 and possibly dead. Below, fairly successful infection. 



6. Empty appressorium and vesicle. On the left infection threads, one 



of which has sent a haustorium into an epidermal cell. 



7. Infection threads growing toward leaf tissues. 



Plate IX. Same as Plate VIII, except Figs. 6 to 10, which are of Arnautka. 

 1 to 5 10 days after inoculation. 

 6 to 10 23 days after inoculation. 



1. Short hyphal segment containing four nuclei. Haustorium in epidermal 

 cell. Hyphae sent out from segment disintegrating. 



2. Disintegrating hypha with haustorium in host cell. 



3. Long hyphae, the tips of some becoming much vacuolated and apparently 

 dying. 



4. Typical appearance of hyphae under epiderm, showing haustoria and 

 some dying hyphal tips. 



5. Hyphae deeper down in leaf tissues showing tendency to aggregate. 



6. Dead host cells and practically dead hyphae. 



7. Hyphae typical of those in subepidermal wefts showing knoblike branches 

 which are often quite characteristic. 



8. Small, partly ruptured pustule. 



9. Single uredospore. 



10. Subepidermal weft showing unsuccessful attempt at pustule formation 

 and a number of abortive spores. 



