PROTECTING PLANTS 189 
and dwellings for such pests and vermin as become established 
in them. The following directions are from Cornell Bulletin 
283 (from which the formulas in the succeeding pages, and 
most of the advice, are also taken) : — 
“No general formula can be given for fumigating the different 
kinds of plants grown in greenhouses, as the species and varieties 
differ greatly in their ability to withstand the effects of the gas. 
Ferns and roses are very susceptible to injury, and fumigation 
if attempted at all should be performed with great caution. 
Fumigation will not kill insect eggs and thus must be repeated 
when the new brood appears. Fumigate only at night when 
there is no wind. Have the house as dry as possible and the 
temperature as near 60° as practicable. 
“ Hydrocyanic acid gas is a deadly poison, and the greatest 
care is required in its use. Always use 98 to 100 per cent pure 
potassium cyanide and a good grade of commercial sulfuric 
acid. The chemicals are always combined in the following 
proportion: Potassium cyanide, 1 oz.; sulfuric acid, 1 fluid 
oz.; water, 4 fluid oz. Always use an earthen dish, pour in 
the water first, and add the sulfuric acid toit. Put the required 
amount of cyanide in a thin paper bag and when all is ready, 
drop it into the liquid and leave the room immediately. For 
mills and dwellings, use 1 oz. of cyanide for every 100 cu. 
ft. of space. Make the doors and windows as tight as pos- 
sible by pasting strips of paper over the cracks. -Remove the 
silverware and food, and if brass and nickel work cannot be 
removed, cover with vaseline or cloths. Place proper amoun. 
acid and water for every room in 2-gal. jars. Use two or more 
in large rooms or halls. Weigh out the potassium cyanide in 
paper bags, and place them near the jars. When all is ready, 
drop the cyanide into the jars, beginning on the top floors, 
since the fumes are lighter than air. In large buildings, it is 
frequently necessary to suspend the bags of cyanide over the 
jars by cords running through screw eyes and all leading to a 
