Sept. 7, 1923 
Puccinia glumarum and Hosts for Variety iritici 373 
centage by the corresponding degree is 1,290. Dividing this sum by 
3, the number of replications, gives 430, which, therefore, is the average 
product representing the comparative susceptibility of Chul wheat, 
based on a possible maximum of 1,000 (Table IV). 
In Table III, the percentage of plants infected and the degree of infec¬ 
tion are shown for the 1917-18 season. The average susceptibility of 
each variety is shown in Table IV, not only for the first season, but for 
the seasons 1918-19 and 1919-20 as well. 
Evidence of the varying susceptibility, even of strains within a variety, 
is shown in the case of the White Winter variety. In Table IV are 
listed five different C. I. numbers 6 of this variety. It will be noted 
that C. I. No. 5219 is somewhat susceptible, while three other strains are 
entirely immune, so far as those experiments show. The White Winter 
selection, C. I. No. 5222, which is quite susceptible, is also morphologi¬ 
cally distinct from the other strains. These results emphasize the state¬ 
ment made by Vavilov (19) that workers should be careful to designate 
the exact botanical classification of host as well as parasite. Vavilov 
suggests that pure lines are desirable in studies of varietal susceptibility. 
6 Accession numbers of the Office of Cereal Investigations. 
