178 FUMIGATION METHODS 
sensitive to treatment than others, but the behavior in 
general did not vary much. ‘The strength of the gas 
used varied from 0.003 of a gramme per cubic foot to 
1.45 grammes per cubic foot. In the first experi- 
ment Dr. Townsend's object was to determine whether 
the ordinary strength of gas used in fumigation 
would be harmful to the seeds. In later experiments 
he determined the maximum and minimum strength 
of gas that seeds could resist under varying condi- 
tions. 
Time is an important factor in this work. Nursery 
stock must be fumigated 30 to 45 minutes or longer 
to destroy all insect life, but in the fumigation of build- 
ingsin which large bulks of grain are stored, time must 
be allowed for the gas to penetrate the mass. During 
this period the grain on the surface is exposed to the 
influence of the gas from the time it is generated. To 
determine the shortest and longest time required for 
grain to respond to the influence of the various 
strengths of gas under different conditions employed, 
the exposures varied from one hour to one year. 
Seeds were also fumigated under varying conditions, 
some being used while perfectly dry in a dry chamber, 
while others were used after being soaked in water, 
and still others were soaked and placed in a moist 
atmosphere filled with gas. After considering all the 
facts Dr. Townsend’s conclusions are concise, clear and 
practical. 
He found that seeds, whether in the dry or moist con- 
dition, are capable of absorbing hydrocyanic acid gas 
from the surrounding atmosphere, whether the amount 
of gas in the atmosphere is large or small per cubic foot. 
