246 BOTANICAL GAZETTE [APRIL 
cyanid of potassium is used for each cubic foot of space to be 
fumigated.® 
In these experiments the strength of the gas varied from 
0.0038" per cubic foot to 1.458" per cubic foot. While in the 
first experiments the object was simply to determine whether or 
not the ordinary strength of the gas used in fumigation would 
be harmful to the grain or other seeds, in the later experiments 
an effort was made to determine the maximum and minimum 
strength of gas that the seeds could resist under the several 
conditions employed. It should be noted that time is an impor- 
tant factor in these experiments. Nursery stock may be fumi- 
gated in thirty minutes, so that all insect life will be destroyed ; 
but in fumigating buildings in which large bulks of grain are - 
stored time must be allowed for the gas to penetrate the mass 
of grain and thus reach the insects that may be scattered 
through it. While time is being given for the gas to penetrate 
the bulk of grain, the grain on the surface of the bulk is exposed 
to the influence of the gas from the time it is generated. Hence 
an effort was made to determine the maximum and minimum time 
required for the grains to respond to the influence of the various 
strengths of gas used under the several conditions employed, 
and with this point in view the exposures varied from one hour 
to one year. 
EXPERIMENTS WITH DRY SEEDS. 
Trial experiments.—In the first experiments dry seeds were 
placed in shallow dishes and exposed for one hour to charges of 
gas varying in strength from 0.258" to 1.452" of potassium cyanid 
per cubic foot. Only a thin layer of seeds was placed in each 
dish, so that the gas came directly into contact with each seed. 
At the end of one hour the seeds were taken from the fumigat- 
ing chamber and placed in hydrant water for twenty-four hours. 
At the expiration of this time they were spread upon moist filter 
paper in damp chambers and kept at ordinary room temperature 
of about 18° C. In this, as in all the other tests, control experi- 
ments were used in which the seeds were treated in precisely 
SJOHNSON, Joc. cit. 
om 

