Sept. 15, 1923 
Corticium vagum on the Pea and Bean 
441 
DISCUSSION OF RESULTS OBTAINED WITH THE BEAN 
In steam-sterilized soil Corticium vagum is shown to have a wide 
pathogenic range on the bean of from 9.4 0 to 29 0 C. With unsterilized 
soil, however, the fungus appeared definitely limited in its parasitic 
action under both the higher and lower temperatures tried in the experi¬ 
ments. In fact, under these more natural conditions, serious damage 
was confined entirely to the temperatures of 12.5 0 , 15 0 , 18 0 , and 21 0 , 
with a definite optimum for tissue destruction between 15 0 and 18. As 
with the pea and the potato, it is conceivable that the optimum might 
vary, contingent upon the conditions of the experiment, anywhere 
between 15 0 and 21 0 . 
Fig. 5.—Bffect of soil temperature upon the pathogenicity of Corticium vagum on the bean and upon the 
development of the host in uninoculated soil. The optimum temperature for the bean at the end of 
seventeen days lies clearly beyond the temperature range for the serious pathogenic action of the fungus. 
General cultural experience shows the bean to be a plant which requires 
a high temperature for maximum growth and yield. Reddick (jj) 
obtained the best growth at 28° C., while for germination Reynolds (12) 
found 30° to be the most favorable. Height measurements and dry- 
weight determinations in the present experiments, although not extensive, 
would indicate that the optimum soil temperature for the continued 
growth up to approximately three weeks, lies between 28° and 31 0 . The 
plants came up in all cases at the highest temperatures employed. 
The parasitic relation of Corticium vagum on the bean is especially 
interesting in that the temperature most favorable for the growth of 
