61 
handling the salt solution, and though CS, is not as ‘poisonous, it is 
highly explosive. 
For fumigating individual plants the apparatus needed and method 
of generating the gas was soon ascertained. For small mefon and cab- 
bage plants we had made small paper covers, under which the gas is 
generated. These are pyramidal in shape, the apex being 8 inches 
high, and the paper fastened to the inside of a wood frame 3 inches 
high by 20 inches square, which forms the bottom. This frame is 
sharply beveled on the lower edge, to enable one to firmly plant the 
cover in the soil. A good quality of building paper is used for the top 
and is cut in one piece, so that there is only one seam. The materials 
for these covers cost from 3 to 4 cents, and we are having fifty made for 
£6. In the field the covers are easily handled, as they rest one within 
the other. 
We have found that in using potassium cyanide a small amount in 
solution is much superior to the dry salt, it being more easily measured 
and handled. Furthermore, in first mixing the acid and water and 
then dropping in the salt much of the heat necessary to the generation 
of the gas is lost by radiation before the salt can be thrown in, no 
matter how quickly the generation be performed. By dissolving 
100 grams of KCn in sufficient water to bring the solution up to 
200 ce., when finished a solution is secured which is of good strength 
and one of which different amounts can be easily computed, 2 ce. 
equaling 1 gram KCn. To generate the gas a one-fourth dram 
(8 cc.) vial is filled with the KCn solution and an equal or slightly less 
amount of sulphuric acid placed in the bottom of a 2-dram vial. The 
larger vial is thrust deep in the earth, being careful to place it so that 
the overflowing acid will not strike the plant or cover. The smaller 
vial holding the cyanide is then dropped into the acid, mouth down, 
and the plant quickly covered and the cover firmed down. The capil- 
larity of the one-fourth dram vial prevents a too sudden generation 
of the gas and allows time for placing the cover. The vials are car- 
ried in carriers holding one hundred or more,as desired. These are 
made of a piece of board for the bottoms, in which two hundred holes 
the size of the vials have been drilled, on the bottom of which a piece 
of wire netting is tacked. With sides and a hinged cover these make 
handy and safe trays. No stoppers are used, but a piece of rubber 
packing inside the cover of the tray would serve the same purpose. 
As regards the amount of cyanide to be used and the length of time 
necessary to kill plant lice and other insects, there has not yet been 
opportunity for sufficient tests to give conclusive results. From some 
75 tests made, we believe that a one-fourth dram vial of the above- 
mentioned solution (or about four-tenths gram KCn per cubic foot air 
space) with an equal amount of acid for ten minutes will be found 
entirely satisfactory. In some tests upon young canteloupes which 
