1910.] 



PUBLIC DOCUMENT — No. 31. 



225 



Experiment XVI. 



Kight Exposures for Temperature and Humidity, February 26, 

 21, 28, March 5, 6. 

 riniiigation with .01 gram KCIST per cubic foot ; plants about 

 seven weeks old ; first two sets treated in starlight, third and 

 fourth on a cloudy night, fifth and sixth in starlight, seventh 

 and eighth in moonlight, ninth and tenth in a darkened box 

 at night; plants watered at 8.30 a.m., dry when treated; all 

 the plants vigorous ; conclusions drawn after nine days. 



Comments and Conclusions, 

 by h. t. fernald. 



The experiments were planned so that only one factor should 

 vary at a time. It quickly became evident, however, that many 

 of the factors were beyond control, and therefore entire cer- 

 tainty as to the cause of differences in results could not always 

 be obtained. Thus, the treatment itself had the effect of in- 

 creasing the humidity of the fumigator, and sometimes this 

 change was quite considerable. 



Morrill's experiments on the white fly (Technical Bulletin 

 N'o. 1, Hatch Experiment Station, Massachusetts, p. 50, 1903) 

 indicated that fumigation with from .007 gram to .01 gram 

 KCT^ per cubic foot for three hours should control most stages 

 of this insect, and that three such treatments at intervals of 



