344 



ON THE CULTURE 



longer in the house when the air is still, and the 

 cavities in the roof, particularly those between the 

 squares of glass, filled with moisture. 



The Aphides may be destroyed with a gentle 

 fumigation ; but the Thrips and Coccus Hesperidum 

 require a smoke so strong, that a person cannot 

 distinguish an object further than at the distance 

 of four or five feet. 



When a hot-house is greatly infested, either with 

 the Aphides or Thrips, the fumigations should be 

 repeated every third or fourth night for three or 

 four times, and then one may proceed according 

 to the former directions : the reason and necessity 

 of these repetitions proceeds from a probability that 

 the smoke cannot affect the insect in the egg, and 

 perhaps it may not have much power over them in 

 some other of their states ; therefore a fresh brood 

 may naturally be expected in the course of a few 

 days. 



Some are of opinion that it is of great use to fu- 

 migate hot-houses constantly every eight or ten 

 days, (whether it is required or not in respect of 

 insects,) alleging, that the smoke will contribute 

 to the vigour of the plants : but from this I must 

 beg leave to dissent, as nature seems to stand in 

 need of no such superfluous assistance. I must 

 acknowledge, however, that I have found no incon- 

 venience from this practice, when used with the 

 moderation here described. The expense attending 

 it is very inconsiderable, as tobacco grown in this 



country will answer the purpose very well. 

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