1927] 
Control of European Vine-moths 
151 
dimensions were 1.25 m. x 1.25 m. x0.65 m. On its four sides 
a flap 12 c.m. wide was planned to insure against leakage of gas 
during fumigations, by placing earth or stones or other weighty 
materials on the flaps. The galvanized iron can was 95 c.m. 
high with a diameter of 60 c.m. The galvanized iron can was 
originally thought of because of the certainty of its being airtight 
and rain proof, very important considerations for overnight 
fumigations. It has the further advantage in winter fumigation 
work over the canvas tent in that the temperature within it 
rises several degrees above that of the outside air. Tests made 
to determine this point showed an increase of 2 degrees C. after 
an exposure of one hour, when the outside temperature was 10 
degrees C. and an increase of 5 degrees C. after an exposure of 
two hours with the outside temperature at 16 degrees C. 
Dosages and exposures . — The cubic content of the tent was 
940 litres. In order to secure a concentration of HCN gas equal 
to 1% of the volume of the space within this tent, it was cal- 
culated that approximately 45 grams of Ca (CN) a should be ap- 
plied. For a dosage of 10% volume, therefore, it would be 
necessary to use ten times 45 grams, or 450 grams. Likewise it 
was found that 12.5 grams of Ca (CN) 2 would produce a 1% 
volume concentration of HCN gas when applied under the gal- 
vanized iron can, the cubic content of which was 270 liters. 
The dosages used in the 71 experiments varied from 0.275% 
volume to 10.00% volume, each dosage being tried at least 
twice with a given exposure. The exposures were varied also, 
these being dependent on the dosages. The exposures were for 
periods of 30 minutes, 45 minutes, 1, li, 2, 2i and 3 hours. Some 
overnight exposures were also tried. In general, smaller dosages 
were used in the long exposures and larger dosages in exposures 
of short periods. 
The treatments. — Dr. Stellwaag, in the experiments referred 
to above, found that the grapevine is an extremely delicate and 
tender plant and that it is unable to withstand heavy concen- 
trations of HCN gas. In view of this, coupled with the desire 
to cause as little injury as possible to the plants, the dosages 
used in the first twenty experiments were less than 1% volume. 
Beginning with a dosage of 0.275% volume, with an exposure 
