FUMIGATION. 169 



flower. Even mealy bugs and Orthezia insignis are said to be destroyed 

 without the least injury to so delicate a plant as coleus. A description 

 of the process, taken from an American source, was published in the 

 Gardener's Chronicle for 16th July last, and from this I glean the 

 following particulars : — Three parts 'Cf acid to two of boiling water are 

 used, and the cyanide added while the acid-water mixture is bubbling 

 with heat ; this secures a very rapid evolution of the gas, and necessi- 

 tates the use of a large generation vessel to prevent slopping over the 

 sides. The exposure is a short one, the house being opened as much as 

 possible from outside as soon as twenty-five minutes have expired. For 

 each cubic foot of free space enclosed, one and eight-tenths grains of 

 cyanide are used ; which, if troy grains are intended as seems most 

 probable, is equivalent to one avoirdupois ounce to 200 cubic feet. 

 " All damp must be driven out of the house, and the plants should be 

 quite dry in their foliage before commencing to fumigate them with 

 the cyanide, because if there is any moisture on the leaves and young 

 growths, they are liable to get scorched. All being dry and in good 

 order, the process may be carried out with perfect safety to the plants ; 

 and houses full of palms, ferns, roses, violets, carnations, and other 

 tender plants and flowers have been treated as described with the most 

 successful results, the insects being destroyed and neither a flower nor 

 a leaf hurt iu the least." 



To what extent this innovation in glass house fumigation has come 

 into practice I do not know, but its discussion in several gardeners' 

 papers has attracted wide attention to it. Opinion concerning its prac- 

 tical value is diverse, largely on account of the risk both to the operators 

 and the plants ; but there seems to be no question that when certain 

 precautions are fully observed the results will be all that is claimed 

 above. However, 1 do not refer to the use of the gas in glass houses 

 here in order to recommend its general adoption in this country. I am 

 not prepared to do that, not having experimented to satisfy myself just 

 what precautions are necessary to ensure entire safety to the plants. 

 But I do suggest that nurserymen and florists who have fumigation 

 chambers, and gardeners who have closets or rooms they could safely 

 use as chambers, experiment on pest-ridden plants to which they can 

 afford to risk injury, and demonstrate to their own satisfaction the 

 economy of the process. The essential feature to prevent injury to the 

 plants seems to be the absence of moisture, both in the air and on the 

 foliage. Our climate is so mild a one that it is unnecessary to have 

 glass houses here built and kept in such good repair that they are 

 approximately gas-tight ; and it naturally follows that the proportion of 

 them which may be closed tight enough to answer as fumigating 

 chambers is not large. Further, owing to the exceedingly poisonous 

 character of the gas, its use in conservatories attached to dwellings is 

 dangerous. For these two reasons it is unlikely that the gas will 

 become a popular glass house fumigant in the colony. Still, florists, 

 curators of public gardens, and gardeners on large estates may find its 

 use, particularly in special chambers, a welcome improvement on their 



