178 FUMIGATION METHODS 



sensitive to treatment t^an others, but the behavior in 

 general did not vary much. The strength of the gas 

 used varied from 0.003 f a gramme per cubic foot to 

 1.45 grammes per cubic foot. In the first experi- 

 ment Dr. Townsend's obje<5l 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- 

 ings in 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. 



