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Psyche 
[June-August 
of 30 minutes, both dosage and exposure were increased to 1% 
volume and treated one hour, but witn no appreciable effect on 
the insects or on the plants. Gradually the dosages were in- 
creased even beyond that fatal to the insects up to 10% volume 
to note the effect of abnormally strong applications of HCN gas 
on the vines. It is interesting to note that even such a heavy 
dosage as 10% volume (450 grams to a space of 940 liters) just 
before the flow of sap had commenced (on March 25, 1926) did 
not prove fatal to the plants, merely “retarded growth” being 
the observation made on the following 12th of April. 
In all the experiments fresh Cyanogas calcium cyanide 
grade “A” dust was used. The exact dosage of the dust, after 
being measured on balance scales, was placed in a foot-pump 
duster and applied under the tent or galvanized iron can. No 
difference was noted in the results when the nozzle of the duster 
was directed to the bottom of the covering or to its top. In the 
latter case the plants would be covered with a fine coating of the 
dust, whereas when the dust was directed to the ground there 
would be practically no dust on the vines. In either case the 
effect both on the insects and the plants treated was the same. 
To discuss each of the 71 experiments in detail seems un- 
necessary, for the majority resulted in only partial kills or no 
kills at all. Only in nine of the experiments was complete kill 
of the insects exposed to treatment secured, the details of which 
are given in the accompanying table. 
The primary object of Experiments 29, 30, 31 and 32 was to 
see if abnormally excessive dosages, during exposures of 30 and 
45 minutes, under the tent and also under the galvanized iron 
can, would be fatal to the vines. Observations on the condition 
of the plants made on April 12, a short while after the leaf buds 
had burst, showed them to be slightly retarded in growth. No 
injury was caused to any of the plants in their dormant con- 
dition even with such strong applications of the poison. 
Experiment 53 was conducted on a fair, warm and calm 
afternoon. 15 naked pupae were exposed to 3.5% volume (45 
grams of poison to 270 liters of space) for one hour, from 2:15 to 
3:15 p. m., under the galvanized iron can. The nozzle of the 
