468 
Journal of Agricultural Research 
Vol. XXI, No. 7 
tank held at 9 0 had succeeded in getting above the surface. The plants 
were thus removed at a period too early to obtain reliable data as to the 
effects of the fungus on the shoots above the ground. The results of the 
observation made 30 days after planting are shown in Table II. 
The results were surprising, in that stem lesions occurred throughout 
the entire range of temperatures from 9 0 to 27 0 C. No lesions were 
found on the stems grown at a soil temperature of 30°. The greatest 
Fig. 2.—Relation of soil temperature to the severity and to the distribution of the injury on the potato 
stems caused by Corticium vagum (experiment 2). 
degree of injury occurred unmistakably at i8°. The plants in the soil 
held at 21 0 were also severely damaged. 
Decidedly greater damage occurred in the unsterilized as compared 
with the sterilized soil. All plants in the control cans remained free from 
lesions. 
Experiment 3.—The results thus obtained with pure cultures in 
sterile soil show definitely the power of the fungus to produce lesions on 
potato stems through a range of soil temperature from 9 0 to 27 0 C. The 
conditions, however, under which the data were obtained were obviously 
artificial and can provide but a very general idea as to what might be 
obtained in nature. With the view of obtaining a more accurate index 
to the practical problem, natural means of soil infection were used in this 
experiment. 
