1910.] 



PUBLIC DOCUMENT — No. 31. 



225 



Experiment XVI. 



Nlglit Exposures for Temperature and Ilumidity, February 2G, 



21, 28, March 5, 6. 

 Fumigation with .01 gram KCN 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; jdants watered at 8.30 a.m., drv when treated; all 

 the ]^lants vigorous; conclusions drawn after nine days. 



Comments and Conclusions, 

 by ii. t. fernald. 

 I 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 efl^ect 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. HO, 1903) 

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

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

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



