2o8 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 



this field suffer from an excess of moisture, but, on the other 

 hanfl, the moisture supply was deficient during a good part of 

 July and August. 



Greenhouse Experiments. 



Mention has already been made of certain results secured in 

 the greenhouse. The details of this work were mostly carried 

 out by the junior writer but the observations were carefully 

 checked by both of us. While these experiments are not as 

 extended in some instances as might be wished, they do in a 

 large measure confirm and extend the observations made in the 

 field. Their chief value lies in the fact that they were con- 

 ducted under the control conditions and that all inoculation 

 experiments of growing plants and other tests, the nature of 

 which made this precaution necessary, were carried on in pots 

 of soil that had been thoroughly sterilized with steam under 

 pressure of at least 20 pounds. In growing plants for inocu- 

 lation experiments seed tubers were used which showed no 

 evidence of Rhizoctonia on their surfaces, but as a further 

 precaution were disinfected before planting. 



Soil inoculation. Three series of pots containing a dozen 

 or more in all were inoculated by burying just beneath each 

 seed tuber small sclerotia or masses of fungous threads from 

 pure cultures of Rhizoctonia. In no case did the fungus seri- 

 ously attack the young plants or young tubers but numerous 

 sclerotia were found on the latter when harvested. In a simi- 

 lar experiment described later and designed to test the effect 

 of lime on the soil more positive results were obtained both 

 with limed and unlimed soils. In the last mentioned test the 

 more recently isolated culture of the fungus appeared to be 

 more virulent. It is possible that in the experiments described 

 above the strain used had been so long in culture that it had 

 lost its virulence. 



Inoculation of young, growing tubers. Young, growing 

 tubers on plants in pots were inoculated with pure cultures in 

 several instances. In some cases the surfaces of the tubers 

 were first injured by pricking with a sterilized needle and in 

 others small masses of the fungus mycelium were simply laid 

 against the uninjured skin. Regardless of the manner of inocu- 

 lation all plants inoculated in this way developed cases of 



