160 
mercially prepared fumigating papers are suspended in strips and 
lighted when ready to fumigate. Dry preparations are placed in 
shallow dishes and ignited. It is sometimes advisable to add a few 
drops of kerosene to facilitate their burning. The extracts are e\ap- 
orated over a lamp, or, like the sulphur paste, are painted on the 
steam pipes. They evaporate or burn slowly, producing a powerful 
vapor. As a rule it is best to fumigate in the evening, keeping the 
houses closed over night. Most insect pests of the greenhouse may 
be controlled by thoro and oft-repeated fumigations with one of these 
extracts. 
