222 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



obviating the necessity of entering the units to adjust the ventilators. 

 Furthermore, the ventilators, in addition to being screened, open into 

 the corridor and not directly out of doors, thus reducing to a minimum 

 the possibility of a wind storm injuring the plants or permitting the 

 escape of insects by blowing off the opened ventilators of the units. 

 The corridor is ventilated at the apex of the room by the usual type of 

 ventilators used on greenhouses. To secure proper circulation each 

 unit is also provided with a small sliding window 10 inches by 16 

 inches thoroughly screened with copper wire mesh. The sill of each 

 window is eight inches from the floor. These units are so arranged that 

 any one can be fumigated independent of the others. 



A record of the contents of each unit is suspended near the outside 

 of the door entering the vestibule of each unit from the corridor. This 

 record indicates the Federal Horticultural Board number, date of 

 quarantine, name of plant or plants, origin, object of quarantine, and 

 prescribed treatment. Plants are not removed from a unit or new 

 plants substituted without the approval of an inspector of the Federal 

 Horticultural Board. Long white coats are used by anyone entering 

 the units. 



Two additional units, 14 by 20 feet and 18 by 20 feet, are maintained 

 for the purpose of carrying material released from quarantine and 

 awaiting orders for distribution. 



Description of Apparatus Used for Sterilizing Plants and 



Plant Products 

 "Briefly, this apparatus consists of a fumigation chamber or retort 

 [Plate 13] (A), an auxihary chamber or generator (B) for the genera- 

 tion of the gas, and an air pump (C). An additional air pump (D) is 

 also a part of this apparatus, although not necessary for fumigation. 

 One end of the fumigation chamber or retort is permanently closed, 

 while the other end is provided with a heavy iron door swung on a 

 hinge and held in place by six clamps. The gasket which is embed- 

 ded in the door comes in close contact with the flange of the retort, 

 and when properly greased and clamped prevents air from entering 

 the chamber during an exposure. This retort lies with its longest 

 axis in a horizontal position. On the upper side of the retort there 

 are four openings: The one nearest the door (1) is provided with a 

 vacuum gauge, which registers the degrees in pressure in units equiv- 

 alent to inches of mercury; the second opening (2) is fitted to an 

 exhaust pipe which is attached to the air pump (C), the exhaust 

 leaving the pump at 2a; the third opening (3) is used to permit 

 the air to enter the chamber at the completion of an experiment, 

 while the fourth opening (4) is fitted to a pipe which leads to the 



