EXPERIMENTS IN FUMIGATION. 27 1 



nurseries are not provided with any sort of fumigating house. 

 It is rather difficult for the average nurseryman to weight out 

 the small quantity of cyanide necessary to use in a small box 

 because he is not equipped with sensitive scales or balances for 

 the purpose. If some volatile liquid could be used that he could 

 measure in a glass cylinder, it would obviously be a much more 

 simple and convenient matter. 



For the purpose we therefore selected carbon disulphide and 

 carbon tetrachloride for volatile liquids, and sulphuretted 

 hydrogen and chlorine for gases- generated by chemical action. 

 In order to make comparisons, a few tests were made with 

 hydrocyanic acid gas, and untreated trees were kept as checks. 



The trees were fumigated in a long narrow box containing 

 ten cubic feet of space. In order to epsure a more uniform 

 distribution of the gas, two generating dishes were used, one 

 being placed near each end. The liquids were volatilized in 

 shallow pans placed upon crossboards near the top of the box 

 and above the trees. For the other materials deeper generators 

 were necessary, and ordinary pudding dishes served the purpose 

 nicely. A piece of glass was set in each end of the cover so 

 that the action of the materials in the generating jars could be 

 watched from outside. 



As some of these materials were being used in this work for 

 the first time, no data were available as a basis from which to 

 compute quantities. In some cases Mr. Heath figured out the 

 quantities of chemicals necessary to generate a volume of gas 

 sufficient to fill the box if all the air was displaced. We could 

 then divide these amounts by two or by four, as seemed best. 



With carbon disulphide we had, of course. Smith's* and 

 Garman'sf experiments in destroying the melon aphis and the 

 experiments of various entomologists in fumigating stored grains 

 to guide us. The writer once purchased some plants of red- 

 twig dogwood for the garden, and when delivered at the house 

 they were found to be slightly infested with San Jose scale. 

 The plants were placed in one of the set laundry tubs in the 

 cellar, an unmeasured quantity of carbon disulphide poured in, 

 and the whole tightly covered for about twenty-four hours. 



* New Jersey Agricultural Experiment Station Bull.- 109, p. 32, 1895, and 

 121, p. II, 1897. 

 t Kentucky Agricultural Experiment Station Bull. 53, p. 144, 1894. 



