298 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
tion, they still retained their form as in life. On subsequent examinations 
I found the mites did not shrivel up until the buds began to dry. The 
immersion at the lowest temperature of 115° F. for five minutes would, I 
think, be a safe one, and would not injure the plants. Some foliage 
(Pear and Plum) will stand a temperature of 180° without apparent 
injury. I fear, however, that although this method has met with perfect 
success in the laboratory, it would be impossible to carry it out on a 
large scale in the field. In the first place the plants would require to be 
lifted and the branches soaked in the water (syringing would not be 
effectual) ; and secondly, I believe it to be impossible to maintain the 
requisite temperature with any degree of success. It is possible, however, 
that this method may be found of service in treating small bushes of 
doubtful character. Mr. C. D. Wise, the manager of the Toddington 
Fruit Company, has recently given this method a trial on a larger scale ; 
and I find on examining the buds that the mites were all apparently 
killed, but whether the eggs also were destroyed it is not yet possible to 
say. No definite results can be obtained until towards the end of the 
year. 
Gas Treatment.— T\iQ first experiment in this country with hydro- 
cyanic acid on this pest was conducted at Woburn,* the method adopted 
being practically the same as that employed in other countries for the 
destruction of scale insects, &c. (see " Injurious Scale Insects of the British 
Isles," Newstead. Joubnal R.H.S., vol. xxiii. p. 255, 1900). The 
materials required are cyanide of potassium, sulphuric acid, and water. The 
gas is generated by pouring the dilute sulphuric acid upon the cyanide, which 
must be previously placed in a glazed earthenware vessel of some kind. 
At Woburn the gas was confined by placing a box, covered with tarred 
felt, over the growing plant ; the proportions used being 1 ounce of 
potassium cyanide, 1 ounce of sulphuric acid diluted with 2 ounces of 
water, to every 150 cubic feet of space. This treatment- proved a com- 
plete failure, as the plants were afterwards found to be as badly infested 
as before. 
In the " Journal of the South-Eastern Agricultural College, Wye, 
Kent" (see p. 303 following) is a preliminary report, by Mr. H. H. 
Cousins, on the fumigation with hydrocyanic acid for the Black Currant 
Mite, two thousand diseased bushes being treated as follows : — " The 
bushes were tied in bundles and placed in a heap on the ground. Four 
hurdles were arranged as a support, and the whole covered with a 
waterproof cloth. A small vessel was placed on the ground in the centre 
of the heap of bushes. One hundred cubic centimetres of water (about 
4 oz.) were added, followed by an equal volume of strong sulphuric acid. 
Thirty-six grammes (about 1^ oz.) of commercial 98 per cent, potassium 
cyanide was wrapped in thin blotting paper, and dropped cautiously into 
the vessel of acid. The hand was at once withdrawn ; the canvas care- 
fully pressed down all round with lengths of timber. After one hour the 
cloth was removed and the operation was complete." Mr. Cousins further 
states : " A careful microscopic examination failed to show a single living 
mite. All were dead." With regard to the " treatment of established 
bushes," he goes on to say : " We have had successful results with large 
