May, 1922] 



RAINES VEGETATIVE VIGOR OF THE HOST 



231 



higher incidence of infection in the vigorously growing plants of group F 

 and have converted it into an apparently lower susceptibility. It is notice- 

 able that the pustules were larger in experiment V than in the other four 

 experiments. 



Variation in the Incidence of Rust Infection with Variation in the Growth 

 Vigor of the Host Plant, due to Constitutional or Racial Differences 



In soil-culture experiments IV and V, when the 100 variables of each 

 group were arranged in order of dry weight, the series divided into five 

 equal parts of 20 variables each, and the average weights and degrees of 

 infection of these sub-groups determined, a certain relation was apparent 

 between the relative weight attained by a plant and the incidence of rust 

 infection on it. The figures obtained in this analysis of the data are pre- 

 sented in table 13. 



TABLE 13 



Experiment I V 



Experiment V 



The figures show that there was considerable variation in the growth 



