[newton] wheat stem RUST 159 



Triticum durum 



Ac— Acme, C. I. 5284 (S.D. 284). 



Arn— Arnautka, C. I. 4072 (S.D. 150). 



Mnd— Mindum, C. I. 5296 (Minn. 470). 



Spm— Speltz Marz, C. I. (xMinn. 337). 

 Triticum monococcum 



Enk— Einkorn, C. I. 2433. 

 C. I.=U.S. Dept. Agr. Cereal Investigation Office number. 



Table II. — Explanation of symbols used to indicate types and degrees 



of infection of wheat varieties by Puccinia graminis. 



0. Immune. 



No uredinia developed; hypersensitive (sharply chlorotic) 

 flecks sometimes present. 



1. Very Resistant. 



Uredinia minute and isolated; surrounded by sharp, con- 

 tinuous, hypersensitive areas. 



2. Moderately Resistant. 



Uredinia isolated and small to medium in size; hypersensitive 

 areas present; pustules often surrounded by green islands. 



3. Moderately Susceptible. 



Uredinia medium in size; coalescence infrequent; develop- 

 ment of rust somewhat subnormal; true hypersensitiveness 

 absent; chlorotic areas, however, may be present. 



4. Very Susceptible. 



Uredinia large, numerous and confluent; hypersensitiveness 



entirely absent. 

 Miscellaneous Symbols. 

 (;) Chlorotic flecks, 

 (x) Mixture of strains. 



Any particular collection usually comprised a mixture of forms 

 which first had to be separated by cultural experiments. Each form 

 was then cultured separately upon all the differential hosts, and this 

 operation was repeated until constant results were obtained. The 

 reactions towards all of the wheats were then compared with the 

 reactions of the forms described by Stakman and Levine. In all 

 cases they were found to coincide with the reactions of one or other 

 of the forms described by these authors, and consequently the same 

 strain numbers were adopted. 



The methods of inoculating and culturing the rusts were similar 

 to those described by Stakman and Piemeisel (59). In recording the 



