66 
Journal of Agricultural Research 
Vol XXIV, No. 1 
ized soil, but at the same time the resistant tomato was very resistant 
in the seedling stage. He did not state the temperature at which the 
plants were grown, however, and temperature is a potent factor in the 
development of cabbage yellows. At 23° to 32° C. seedlings of the 
resistant strain of cabbage show a high percentage of yellows, but the 
plants which escape the disease usually remain healthy. W. H. Tisdale 
(j^) found the resistant strain of flax to be highly resistant even in the 
seedling stage. 
The upper limit for the growth of Fusarium conglutinans in pure 
culture is about 35° C., yet it produced 100 per cent yellows in plants 
grown at this temperature in artificially inoculated soil. As previously 
stated, the temperature of the first inch of soil at 35"" registers from 1° to 
lower than the water in the tank, and it may be that the fungus 
made its successful attack upon these roots in the first inch of soil. 
The data presented in Table V and figure 6, especially those for arti¬ 
ficially inoculated soil, show that the highest percentage of yellows 
occurred at temperatures above that most favorable for the seedling. 
This indicates that resistance is probably broken down at these higher 
temperatures. However, the chief difficulty in determining to what 
extent the increase in percentage of yellows at higher temperatures is 
due to “breaking down’’ of resistance is the fact that the nature of the 
resistant character has not been analyzed. Until its true nature has been 
determined, it will be impracticable to learn by the common method of 
testing for resistance in plants, that is, by subjecting both host and 
parasite to the different temperatures, just how much temperatine 
affects the resistant character. However, the results obtained with 
artificially inoculated soil indicate that either the host becomes less 
resistant or the fungus more pathogenic at the higher temperatures. 
The latter condition was not in evidence with susceptible plants, but 
the decided stunting of the plants would seem to indicate that they may 
be less resistant. 
