472 
Journal of Agricultural Research 
Vol. XXI, No. 7 
With the exception of the stems in one pot of sterilized soil, all control 
plants were found to be free from both lesions and fungus. The presence 
of the fungus in the one control pot resulted, apparently, from inadequate 
sterilization of the seed. 
Experiment 5.—In this experiment, which was started at the time 
of early potato planting in Wisconsin, an attempt was made to approach 
as nearly as possible the exact conditions found in the field in normal 
potato culture. Surface soil was obtained directly from the field at the 
DZG/Pftt CfA/T/6/?/)P£ 
Fig. 4.—Relation of soil temperature to the severity and to the distribution of the injury caused on potato 
stems by Corticium vagurn (experiment 4). 
time of planting, May 17, and was placed, after mixing and without 
sterilization, into sterile cans. No serious modification of the water 
relation or the structure of the soil resulted. The soil was compara¬ 
tively damp, showing a water content at the time of planting of 24.8 
per cent of the dry weight. 
All tubers used for seed were selected for a uniform and an abundant 
occurrence of sclerotia and for the absence of all bruises or scabbed 
areas which might function in the introduction of complicating organisms. 
In order to eliminate organisms loosely adhering to the surface of the 
