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Insects in greenhouses which attack the leaves of plants, 
and do not live in the soil, fumigation with hydrocyanic 
acid gas is the best general remedy. It is made up as 
follows :—2 ozs. cyanide of potassium, 4 ozs. sulphunc 
acid, and 8 ozs. of water. Estimate cubic space of green- 
house and use this preparation for each 1,000 cubic feet 
of space, doubling the quantity for 2,000 cubic feet, and 
so on. First close up all windows and doors and any 
holes should be securely filled up. One window should 
alone be left open for purpose of introducing the mix- 
ture, which is extremely poisonous to man and all forms 
of animal life, but does not injure plants. Use at dusk 
when the plants are dzy, and the temperature of. the 
greenhouse should xot exceed 60 F.—the best temperature 
is 50 F. Do not use when there is a bright light (day- 
light). Pour the water into a jar first, and then add the 
acid slowly. Wrap the cyanide in a piece of blotting- 
paper and drop into the jar with a suitable instrument 
from outside through the window of the greenhouse. 
Then close the window and leave for at least 1 hour. 
Afterwards open all doors and windows from the outside, 
but do not enter the greenhouse until another hour has 
elapsed. Cost about 6d. 
