136 FUMIGATION METHODS 
Gowan will stand one-tenth of a gramme of 98 per 
cent. cyanide per cubic foot of space for fifteen minutes 
without material injury. This will kill about 90 per 
cent. of the plant-lice, but will not kill thrips. The 
use of the gas for carnations needs to be more carefully 
investigated before it is recommended. ‘The same is 
true of chrysanthemums, on which it has been tried 
with only partial success, the young growth being 
very sensitive. 
Grapes under glass.—The gas has been used with 
success in New Zealand for the mealy bug, Dadtylopius 
adonidum 1,, at the rate of one-third of an ounce 98 
per cent. cyanide to 100 cubic feet. This is equivalent 
to nine-hundredths gramme per cubic foot. The gas 
is liberated after dark and left in till next morning, 
when thorough ventilation is given. It largely 
escapes, however, during the night. The treatment 
is said not to injure the plants in the least. 
Tomatoes.—Dr. J. Fisher, on October 29, 1898, 
reports using the gas for white fly (4leyrodes sp.) on 
tomatoes. ‘The gas from one ounce of pure cyanide of 
potassium for each 1,000 cubic feet, left in the house 
over night, killed all the insects without injury to the 
plants. This method should receive careful trial by 
other experimenters. 
Other experiments in greenhouses.—For some years 
in the large greenhouses connected with the Massa- 
chusetts Agricultural College considerable difficulty 
has been experienced with mealy bugs and various 
species of scale insects on large vines, palms, begonias, 
orange trees, acacits, etc. After a thorough trial of 
