~ A l   4
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Bisuhohide of Carbon and Ifydwocycmic Acid Gas. 149   g
were found to have been badlyuinjured by the gas. N0   ,VA‘   I
living aphides could be found, but the twigs and leaves   VV.AV.· _ H
were studded with their dead bodies.     t··i j Q
In the above experiment the quantity of material-  
used was too large and the exposure too long. Four min- i Q 
utes would have been ample time to kill the aphides.   i·i__  
Notwithstanding the injjiry to the twigs the bush quickly  
recovered and subsequently made a fine growth, whereas  
it had previously ceased to grow, and would probably not  
have increased in size at all if the aphides had been al-  
lowed to remain. »  
I believe from _my experience with it that this gas  
treatment will yet commend itself to gardeners as a means  
of checking the spread of injurious insects from infested  
centers. It is certainly the quickest and most effective  
method known to me of exterminating the insects infest-  
ing single plants. »  
Both bisulphide of carbon and hydrocyanic acid gas  
are injurious to man, and in using either one must be  
very careful not to inhale the fumes. The fumes of both  
escape quickly, hence it is necessary to shut the tent or  
box promptly after introducing the substances producing L. 
the gases. The bisulphide, it must be remembered also,  
is inilammable. ‘ V `  
The bisulphide of carbon is slower in accomplish-  
ingthe destruction of insects than the other, and must j  
be watched to make sure that treated insects do not  
escape after being simply stupefied. Under a tub of  
medium size a tablespoonful should be allowed to act for  
an hour and a half. Two tablespoonfuls may be made to  
do the work quicker, but this quantity can be left, as I ,. 
determined in 1892, about enclosed vines for an hour L  
and a half, without doing the plants any injury.    
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