204 
DISEASES AND AFFECTIONS OF PLANTS. 
apertures of exit stopped, the results of filling the erection with smoke of black 
shag tobacco rarely admits of doubt ; but in the open air, unless each plant be 
covered with a close hood from top to bottom, the mere propulsion of smoke is of little 
avail. Strong infusions of tobacco, and a liberal dusting with potent Scotch snuff, 
will in a degree relieve, but both the one and the other may injure, and certainly 
will disfigure, the blossom and foliage. Perhaps early and repeated close prunings- 
back to a clean bud would be the best remedy — one which would retard the season 
of bloom till that of the insects had passed by. But another and very clean appli- 
cation has been recently urged, namely, a watery solution of sesquicarbonate of 
ammonia (common smelling salts). 
This suggestion must be met, first, by throwing a doubt upon its efficacy, unless 
it were applied so strong as to destroy the plant itself ; and secondly, by reminding 
the gardener that, unless he project the fluid forcibly over and among every leaf or 
mossy integument, by the syringe, he will fail to destroy the pest ; but in a chemical 
point of view the attempt will ruin the instrument, since ammonia, either pure or as 
carbonate, or sesquicarbonate, will infallibly act upon the copper and brass, and pro- 
duce a solution of ammoniuret, which is colourless till it become blue by exposure to 
air. Thus the syringe will be corroded, and rendered useless. 
Sesquicarbonate of ammonia dissolves in somewhat less than four times its weight 
of water, heated to 60 or 65 degrees ; its price varies from Sd. to Is. 3d. per lb., 
and therefore might easily be found expensive ; for a weak solution, i.e., of 1 oz. to the 
quart, could be of little avail. As to the caustic liquor of pure ammonia, it would 
prove fatal ; a Gardenia radicans infested by the scale was put under a bell-glass, 
and with it about a tea-spoonful of liquor ammonias fortis ; the foliage in a few seconds 
became of an intense blue-green, beautiful in appearance ; the glass was raised and 
the plant removed ; but its change was mortal. 
Plants are susceptible of poisons. A small orange-tree, alike infested, was lightly 
brushed over the stem and the axils with a weak solution of arsenic ; it was killed 
almost immediately. The change was exceedingly rapid. 
Two species of Aphis are not easily assailable by tobacco ; the one is the black 
aphis of the cherry-tree, which covers and much injures the summits of young shoots. 
A simple but effective remedy is found in a sort of batter, made with stiff soil or 
clay and water. By dipping the infested parts of the tree in this " slip" (as it is 
called in the potteries) till they are coated with it, the insects are cased, and entirely 
destroyed. The black Aphis of the garden bean is much checked by the simple and 
usual operation of topping. 
The red spider (Acarus) is most mischievous, particularly with such plants as 
Thunbergia, and the kidney bean. The name is given alike to every variety, whether 
the insect be white, brick-red, or black. It punctures the undersides of the leaves, 
arrests their growth, and entirely changes their colour. Sprinkling, and a highly 
vaporous atmosphere, are the best applications. Of sulphur as a wash, and in the 
form of vapour, raised by sprinkling brimstone on the warm flues, much has been 
