132 FUMIGATION METHODS 



on the surrounding plants. Paper used for this pur- 

 pose can be rolled together, laid away, and is ready for 

 future use. When everything is in readiness, doors and 

 ventilators should be closed, and the cyanide lowered 

 into the vessels by loosening the strings. The gas is 

 given off almost immediately and a small quantity will 

 leak out of the house; but if the room is reasonably 

 tight the greater portion of it will be kept within for 

 a time sufficient to destroy the pests. When the 

 proper time has elapsed, varying, of course, for different 

 plants, the ventilators should be opened from the out- 

 side, so that the gas can escape as rapidly as possible. 

 After free circulation is obtained by opening the doors 

 and ventilators, all traces of the gas will have dis- 

 appeared from the house in from thirty to forty 

 minutes. The house can then be closed if desired. 

 The residue left in the jars should be emptied, as 

 previously described. 



Boxes for fumigating small plants. Where it is 

 desirable to fumigate several hundred small plants, 

 small boxes, such as described in Chapter XI. , can be 

 used to good advantage. In most cases a special box, 

 such as shown in Figs. 47 and 48, is desirable. The 

 box should be as nearly air-tight as possible, with a 

 removable cover or trap-door which can be quickly 

 closed. A special box, shown in Fig. 71, was con- 

 structed and used by Prof. K. D. Sanderson for the 

 fumigation of small plants. Small wire or slatted trays 

 can be used to good advantage for the fumigation of 

 cuttings, such as coleus and various other plants. 

 Potted plants can be fumigated in the same box if 

 necessary. 



