APPLIANCES 19 



to them by means of bellows. A knapsack apparatus 

 designed on this principle is procurable, as also are 

 other more powerful appliances, some of which are 

 worked by horse-power. It is important that the 

 powder used should be in a very fine state of division, 

 and that it should be quite dry : on the other hand, 

 the trees should be slightly wet, so that the powder 

 may stick to them. The dusting of trees, therefore, is 

 best done in misty weather, or after a heavy dew. 



Liquids may be injected into the soil by means of 

 a Vermorel's injector, which is a syringe with a long, 

 sharp nozzle, which can be thrust into the soil to 

 various given depths. 



