94 FUMIGATION METHODS 
fumigator is employed, however, this difficulty is over- 
come, as the cubic content is constant and the amount 
of chemicals used does not vary. The danger of error 
iseliminated when a box or house is used. It matters 
FIG. 47—BOX USED BY SOME NURSERYMEN IN THE SOUTH 
(AFTER SHERMAN) 
not whether one or several thousand trees are placed 
in the enclosure, the amount of gas generated must re- 
main constant. 
Small boxes.—Many nurserymen find small boxes 
very useful. Fig. 47 is a box used in North Carolina. 
The details for construction are given by Prof. Frank- 
