SC6  ReEportT OF THE DEPARTMENT OF ENTOMOLOGY OF THE 
same time uniform chemical action is obtained and spattering 
avoided. 
Although the tests indicate that a formula of 1-14-83, that is 
1 part by weight of KCN, 13 times as much acid and 38 times as 
much water by volume as of KCN, gave best reactions, the 
formula generally recommended for orchard and nursery work, 
viz.: 1-14-24, that is 1 part by weight of KCN, 14 times as much 
acid by volume and 14 times as much water as acid gave as 
good results under most conditions, hence if preferred can be 
followed. If too violent action results more water can be added. 
ABSORPTION OF THE GAS. 
From results obtained in fumigation of forcing houses, we 
were led to assume that the hydrocyanic acid gas either had a 
tendency to bank or was rapidly absorbed as it came in contact 
with moist soil. 
Some tests made during winter of 1899 and the following 
winter on diffusion of gas showed that about 50 per ct. of the 
gas was absorbed by the moist earth. These tests also showed 
that under cloth-covered fumigators the diffusion was quite 
uniform. 
Penny! has shown that in the presence of moist soil over 50 
per ct. of the available gas present in a cubic foot of space is 
absorbed. For example, if .15 grm., an amount recommended 
for fumigation of nursery stock in closed boxes, is used in 
orchard work where it comes in contact with moist earth, only 
075 grm. of this amount becomes available for killing the scale- 
insects. 
These conditions, together with failure, in some cases, to kill 
all the scale-insects on low branches and at base of trees, indi- 
cate that double the amounts of KCN generally recommended 
for fumigation of nursery stock should be used in orchard work, 
at least if complete extermination is the object sought. The 
foregoing tests show that on fairly vigorous orchard trees no 
injury to tree will result from use of this increased amount of 

*Del. Coll, Agr. Exp. Sta. 12th Ann. Rept. p. 229, 
