134 FUMIGATION METHODS 
One hundred and fifty to two hundred plants with 
fronds in all stages of development have been thus 
treated two or three times each year for the past four 
years with no injury to the plants and almost complete 
destruction of the insect. They were treated fifty at 
a time in a fumigating box. 
Adiantum cuneatum and A. ballit have been tried 
on a small scale and were not injured by the treatment. 
Coleus.—Golden Bedder, Verschaffeltii, Shylock, 
and others; 24,000 plants in pots, badly infested with 
the white-tailed mealy bug, Ovthezia insignis. The 
house contained 15,587 cubic feet of space. ‘Treated 
at the rate of one-tenth of a gramme of 98 per cent. 
cyanide of potash per cubic foot of space for twenty 
minutes, one hour after dark. Orthezia all killed and 
plants not injured in the least. All other means of 
destroying the Orthezia had been tried without effect. 
Large numbers of the common mealy bug were also 
killed by this treatment; but it was not nearly so 
effective as for the white-tailed mealy bug. All coleus 
cuttings made by the United States Propagating Gar- 
dens for the past few years have been fumigated before 
being prepared for the cutting bed. 
Double English violets—Marie Louise, Lady Camp- 
bell, and others. For plant-lice and general fumiga- 
tion fifteen-hundredths of a gramme of 98 per cent. 
cyanide of potassium for each cubic foot of space is 
required. ‘The exposure, if made according to direc- 
tions, will not hurt the plants in any stage of growth. 
The gas has been used on a large scale in fumigating 
violets for the past three years with the greatest suc- 
