Division of Botany of the Department of Agriculture, with carbon 

 bisulphid, and Townsend, formerly of the Maryland Experiment Sta- 

 tion, with hydrocyanic acid gas, show that the germinating power of 

 the seed would not be lessened by treatment with either of these mate- 

 rials. As a matter of fact, numerous experiments that have been per- 

 formed in connection with the present work have fully substantiated 

 the results obtained by other investigators. 



Carbon bisulphid seems to be much cheaper for use in the fumiga- 

 tion of cotton seed than is hydrocyanic acid gas. The former at the 

 rate of li pounds per 1,000 cubic feet would cost about 15 cents for 

 1,000 cubic feet, while for fumigation for the same space with hydro- 

 cyanic acid gas at least 10 ounces of potassium cyanide would be 

 required. This would cost about 25 cents, to which must be added 

 about 2i cents for the sulphuric acid, bringing the cost up to nearly 

 twice as much as in the case of the former f umigant. Mr. C. L. Mar- 

 latt and others have remarked about the greater resistance of weevils 

 to hydrocyanic acid gas than to carbon bisulphid. These observations 

 have been fully verified in the case of the boll weevil by investigators 

 who have conducted the work. 



FXTMIGATION EXPERIMENTS. 



In order to test the relative adaptability of these gases, and to deter- 

 mine the conditions under which they may be used effectively, a num- 

 ber of experiments were performed. 



Experiment with hydrocyanic acid gas. 



In this experiment weevils in tin boxes, perforated in such a man- 

 ner as to allow the free access of the gas, were buried at varying 

 depths in sacks containing 100 pounds of cotton seed. The sacks were 

 inclosed in a specially prepared tight box. The cyanide was lowered 

 into the sulphuric acid through a small orifice in the lid. 



As will be noted, the hydrocyanic acid gas, in a strength twice as 

 great as is successfully used for the fumigation of grain, in a treat- 

 ment of five hours did not kill boll weevils covered by from 6 to 10 



209 



