192 FUMIGATION METHODS 
leakage and by surface condensation on the walls of 
the box, or rather by solution in the film of moisture 
adherent to the walls. 
Leffectt of moisture on foliage.—‘‘ Experiments 
were designed to show the effect of moisture adherent 
to foliage. A quantity of maple and cherry leaves 
were held under a hydrant, then shaken to remove the 
excess of water and placed in the diffusion box. The 
amount of adherent water was about two and three- 
quarter pounds. In each trial a fresh lot of leaves 
was used, and a mechanical mixer or fan was used to 
complete the diffusion. ‘Two trials showed an average 
of 54 per cent. as compared with 72 per cent. obtained 
without the wet leaves, or, with the wet leaves, just 
three-fourths as much acid vapor is diffused through 
the atmosphere of the box as without them. ‘This is 
significant as indicating the effect of wet foliage. The 
amount of acid vapor available for killing inse¢ts is 
diminished and the amount acting directly on the 
plants is increased.’’ ‘Thus the necessity of having 
plants either in the nursery or orchard as dry as pos- 
sible. 
Absorbent effect of fresh earth.—‘‘In this experi- 
ment the bottom of the 29-cubic foot box was removed 
and the box was placed over fresh soil; the soil was 
thoroughly packed or tamped around the edges. The 
surface soil thus exposed was 1144 x 13% feet, or about 
20 square feet. The mechanical mixer was used, as 
noted above. ‘The two trials, with closely concordant 
results, show an average of 44.5 per cent. of the normal 
amount of acid vapor as compared with 72 per cent. of 
