Stpt. is, 1923 
Corticium vagum on the Pea and Bean 
437 
Under these severe conditions total destruction of the plumule resulted 
at temperatures of 15 0 and 18 0 C. At 9 0 , while most of the seed germin¬ 
ated normally, only 1 plant out a possible 29 escaped injury. At the 
higher temperatures the severity of attack decreased more rapidly than 
at temperatures below those most favorable for tissue destruction. 
Severe injury, nevertheless, was obtained at 28°. An interesting feature 
of the experiments appeared in the fact that damage to the primary 
roots occurred at temperatures of from 15 0 to 21 0 , although no visible 
lesions were found on the smaller fibrous roots of the plant. 
Pig. 3 .— Effect of soil temperature upon the severity of injury caused to the pea by Corticium vagum. 
DISCUSSION OF RESULTS OBTAINED WITH THE PEA 
Results obtained from the three experiments on the pea agree essentially 
with those obtained by Jones in showing that within the temperature 
limits employed (9 0 to 29 0 C.) neither the high nor the low temperature 
entirely inhibited injury from Corticium vagum . However, in unsterilized 
soil, as in Experiments 1 and 2, the fungus is shown to be definitely 
limited in its pathogenic power at both the high and low temperatures. 
In these two experiments severe damage to the young plants was con¬ 
fined largely to temperatures of from 15 0 to 24 0 , with an optimum of 
approximately 18 0 C. Such favorable conditions for the pathogenicity 
of the fungus produced by sterilized soil, on the other hand, result in a 
much wider temperature range for the vigorous action of the fungus, 
although even under these conditions the most severe tissue destruction 
ranged between 12 0 and 24 0 . An equally definite optimum under these 
conditions was found at 18 0 . 
In the earlier work on the potato (15), injury to the growing point 
of the young potato shoots appeared as a definite function of the rate at 
