820 Journal of Agricultural Research vol. vi, no. « 



the potatoes was made in April, 191 5. None of the unbruised tubers 

 showed any signs of infection, but infection was present in each of the 

 bruised tubers. 



3. In 1 9 14, attempts to artificially infect growing potato plants with 

 F. trichothecioides were made as follows : 



a. One hundred apparently healthy Idaho Rural plants were selected, 

 and the stem of each was punctured at the crown with a needle inoculated 

 with the spores of the fungus. As a check, twenty-five apparently 

 healthy plants of the same variety were selected and their stems punctured 

 at the crown with a sterile needle. 



b. One hundred apparently healthy Idaho Rural plants were selected. 

 The soil was removed to expose one tuber under each plant. One tuber 

 under each plant was punctured with a needle inoculated with the spores 

 of the fungus. As a check, twenty-five apparently healthy plants of the 

 same variety were selected and the soil removed to expose one tuber under 

 each plant, which was then punctured with a sterile needle. 



c. One hundred apparently healthy Idaho Rural plants were selected 

 and the soil removed to expose one tuber under each plant. The stolon 

 of one tuber under each plant was then punctured with a needle inoculated 

 with the spores of the fungus. As a check, twenty-five apparently 

 healthy plants of the same variety were selected and the soil removed to 

 expose one tuber under each plant. One tuber stolon under each plant 

 was then punctured with a sterile needle. 



An examination was made one month later. No evidence of infection 

 could be found in the proximity of the punctures in the stems, the 

 tubers, or the tuber stolons. The punctures made were so large that they 

 could be seen easily in each case, but apparently they had healed over. 

 The checks presented the same appearance. 



As the foregoing inoculations of growing plants had been made rather 

 late in the season (August 21), it was thought that the failure to develop 

 any infection might have been due to the late date on which the inocula- 

 tions were made. Therefore the attempts were repeated in 191 5 as 

 follows : 



1. Fifty Netted Gem tubers which had been inoculated with F. 

 trichothecioides were kept for several days in moist chambers at tempera- 

 tures favorable for the development of the fungus. On June 4, when the 

 decay was well advanced, the fifty tubers were planted in a Station plot 

 in an attempt to infect the growing plants through the seed pieces. A 

 similar number of hills of the Netted Gem variety were planted with 

 disease-free seed pieces as a check. The plants were examined from time 

 to time during the season, cultures being made whenever any evidence of 

 disease appeared, but F. trichothecioides was never obtained. The plot 

 was dug on September 15, when all stems and tubers were examined for 

 evidence of disease. There was no evidence of decay in the harvested 

 tubers, and the stems of the plants were usually white and clean. Six 



