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chamber, provided with a floe for the escape of the gas after the 

 operation. The more air-tight the chamber, the more complete will be 

 the work. It should be fitted with racks to receive removable trays, 

 upon which fruit may be spread. The objects to be fumigated are 

 placed into position, the chemicals are mixed in a leaden or earthen- 

 ware pan and placed on the floor, the door shut, and the room kept 

 closed for from half to three-quarters of an hour. The flue is then 

 opened, and, after a sufficient time (about half an hour) has been al- 

 lowed for ventilation, the door is unlocked, and the plants, &c. removed. 

 It is not advisable to take the subjected plants directly into the open 

 air if the sun is shining. They should be kept for a few hours under 

 shade, which will greatly lessen any danger of damage. 



Mr. 0. P. Lounsbury, Official Entomologist at < 'ape Town, has 

 kindly supplied me with full particulars of the work of the Fumi^ator- 

 inm at that place. From his letters and reports I have extracted the 

 following directions and suggestions: — 



For each 300 cubic feet of space enclosed (and in proportion for 

 greater and smaller spaces) 1 ounce of 98 per cent, potassium cyanide, 

 1 ounce of sulphuric acid, and 2 ounces of water will be required to 

 generate gas of sufficient strength to kill the insects. Double this 

 strength, or the same amount ot materials to 150 cubic feet enclosed, 

 mav be used upon woody plants without danger of seriously injuring 

 them. The greater strength should be employed whenever practicable, 

 as it will ensure the death of the eggs as well as of the active insects. 



Imported plants are usually in a more or less dormant condition 

 which lessens danger of injury. Mr. Lounsbury writes, in his Report 

 of June 1897, 1 Injury to the tips of new growth generally results. This 

 injury is in no wise serious, and is quickly outgrown. The operators 

 consider it a favourable indication, as when such injury results it is 

 quite certain that the gas has been present in sufficient strength to des- 

 troy all of the insects.' 



With respect to fruit, I again quote from Mr. Lounsbury 's letter : 

 ' I had lemons and oranges analysed after treatment, and found that after 

 few hours not more than a trace of the gas remained in the rind. There 

 is much more natural cyanogen in a single seed (so the analyst told me) 

 than what remains in the fruit from fumigation. We have no com- 

 plaints of any effect on the keeping qualities of the fruit.' 



To generate the gas ' the required quantities of cyanide and water 

 are first placed in the generating vessel, the cyanide being broken into 

 small pieces about the size of lump sugar. The operator then adds the 

 acid, pouring it slowly into the vessel to avoid splashing, and imme- 

 diately withdraws.' 



The above treatment is suitable for fruit and hardy plants. Ten- 

 der garden plants are usually imported in Wardian cases, and may be 

 treated separately. We have — in the 4 Wardian case ' — an air-tight 

 chamber ready to hand, in which the plants can be fumigated before 

 their removal. After a large series of experiments with various fumi- 

 gating media, I find that hydrocyanic acid gas remains by far the most 

 efficient insecticide and the least injurious to the plants. But with, 

 delicate succulent plants I find it has to be applied rather differently. 



