-- BULLETIN 186, U. S. DEPARTMENT OF AGRICULTURE. 
here the seeds were examined carefully at several different times | 
to see whether all insects were killed. The viability of the seeds 
was then tested. 
Part of the germination tests recorded in this paper were made by | 
Mr. W. R. Lucas, of the Office of Foreign Seed and Plant Intro-— 
duction, but in most cases tests with treated and untreated seeds 
were carried out by Mr. W. L. Goss, of the Seed Laboratory of the 
Bureau of Plant Industry. 
In these experiments the duration of the exposure and the con- 
centration of hydrocyanic acid were varied in order to determine 
the minimum exposure and concentration of hydrocyanic acid which 
would insure the death of all the infesting insects. It was also con- | 
sidered of interest to determine whether the seeds would be unin- 
jured if exposed longer and with a higher concentration of the hydro- 
cyanic acid than that necessary to kill the insects. The duration of | 
the exposure and the amounts of sodium or potassium cyanid are 
given in the description of the experiments. The 1-1-2 formula 
was used for potassium cyanid and the 1-13—2 formula for sodium 
cyanid. 
The iron fumigation chamber already described was used in most 
of the experiments. In some of the preliminary work, however, 
desiccators or bell jars- were used instead. The essentials of the 
method were the same in either case, and no description of these 
pieces of apparatus seems necessary. 
EXPERIMENTS. 
The summarized results of these experiments are here given in 
tabular form for comparison (Table I). 
TABLE I.—Summary of experiments in fumigating against insects. 
. Kind ofcyanid | Time 
Material. | Infested with— and amount ° Result. Germination test. 
| used. C2R6 
sure 
Avocado: Ars. 
26seeds. One adult avocado | Sodium cyanid, 1 | Insect'dead2--2-= 22 22 out of 26 seeds germi- 
| weevil ( Heilipus 4 gm., in des- | nated. 
| lauri). iccator. 
ZOISCCOStliecs coo eee esa eee @Osoe8. ese | Se |e leet eae ars ue cn ype ee 20 out of 29 seeds germi- 
| nated; 21 out of 25 
germinated in con- 
trol test. 
5seeds... Larvee of avocado wee- |....- doses eee 1 | Allstages dead....) Seed cut up to deter- 
vil (inclosed in a cot- ; mine mortality of in- 
ton - plugged vial) sects and not plant- 
| and broad - nosed ed. 
| grain weevil (Caul- 
ophilus latinasus). 
ZOSCEASS| Seee meme ee ys eee eal er CKURAD ACES 6 |-.--- WOz a soreeeeee No germination. 
1D Yes fs aa era Bee ee ape ee Goss [Epa A se dose es ps Oo. 
6 seeds... Larvee of Conotrache- | Sodium cyanid, | pate ae Osseo eee oe All seeds germinated, 
lus sp. and broad- 4 gms. | | 
| nosed grain weevil, | 
| all stages. | | | 
10seeds.|..... Moss ste teste ce Bae dOse cee ; | No insects alive Do. 
| | out of 50 exam- 
| ined of all stages. 
