5 
are a number of different plants in same house, the amount of 
cyanide to be used should be such that it will not injure the most 
tender variety. Two other factors which are most important are 
the temperature and the humidity in the house. Plants are always 
more readily injured in a house where the temperature is high, 
say 70 or 80 degrees, than they are when the temperature is lower, 
as for example, 60 degrees. The more moisture in the house, the 
more apt the plants are to be injured, so that the house should be 
just as dry as is possible, considering the plants which are in it. 
Some plants can never be fumigated or have never been success- 
fully fumigated. Roses, carnations, and chrysanthemums have, 
in most all cases, been injured by cyanide so that if these plants are 
present, they should be removed from the house about to be 
fumigated. 
Plants should not be watered just before fumigation. In 
fact, it would be well if the plants had not been watered for 
twenty-four hours before the process. The temperature should be 
low and the fumigation must be done at night; even on a cloudy 
day, it is apt to burn the foliage, while some entomologists seem 
to think it advisable not to fumigate on a bright moonlight night. 
The materials used in fumigation with cyanide are potassium 
cyanide, sulphuric acid, and water. The usual formula is 
1 oz. potassium cyanide. 
1 or 2 fluid ounces sulphuric acid. 
3 fluid ounces water. 
Some prefer to use as much as six fluid ounces of water to one 
ounce of sulphuric acid. The more water that is used, the slower 
the gas is generated and the more evenly it is probably distributed. 
The sulphuric acid is slowly added to the water, which is con- 
tained in an earthenware jar, constantly stirring. The earthen- 
ware jar is necessary, inasmuch as metal will be acted upon by the 
sulphuric acid. The resulting mixture will be hot and the cyanide 
is added to it while still hot. The gas is extremely poisonous as is 
also the case with the potassium cyanide. For that reason, it is 
best not to be in the house at the time that the cyanide is to be 
placed in the jars. This can be arranged by putting the cyanide 
in bags tied to a string which is supported from the ceiling by a 
screw eye, thus allowing the other end of the string to be extended 
