128 FUMIGATION METHODS 
cubic foot, and left until morning. The lice were all 
destroyed, and there was no perceptible injury to the 
plants. Indiancorn, from ten to twelve inches high in 
pots standing in one end of the house for experimental 
purposes, was destroyed. 
Preparation of the house.—The very poisonous 
nature of the gas must be considered. ‘The cautions 
cited in Chapters III. and IV. should be heeded. The 
house should be made as nearly tight as possible under 
ordinary circumstances. The ventilators should be 
arranged so several of them can be opened from the 
outside. Plants that will not stand the stronger doses 
of gas, if in pots, should be removed. The room 
should not be fumigated immediately after the plants 
have been sprinkled or watered. The floor of the 
house should not be drenching wet, although it may 
be damp. 
After estimating the cubic contents of the house, 
and the amount of cyanide is determined, the quantity 
needed can be figured out according to the directions 
given in Chapter XIII. for nursery stock. Care 
should be taken, however, to multiply the number of 
cubic feet by the exact fraction of a gramme. For 
instance, 0.25 gramme cyanide per cubic foot is used 
for well-matured and dormant nursery stock, and 0.20 
gramme for orchard trees out-doors; but no such doses 
are used in greenhouses. Very good results have 
been obtained where 0.15 gramme cyanide per cubic 
foot has been used in greenhouses and cold frames for 
the violet aphis. For other insects and plants the 
amount of cyanide varies, as indicated above. 
