The Conchifion. 375 



Tho* Ever-greens are found to imbibe and 

 perfpire much Iefs than other trees, yet is the 

 quantity they perfpire fo considerable, that it 

 has always been one of the greateft difficulties 

 in the ordering of a Green-houfe, to let in 

 frefh air enough without expofing the plants 

 to too much cold. For iince the perfpiration 

 of trees will not be free and kindly in a clofe 

 damp air, the fap will be apt to ftagnate, 

 which will make the plants grow mouldy, 

 or they will be fickly, by imbibing fuch damp 

 rancid vapours : For by Mr. Millers curious 

 obfervations on the perfpiration of the Plan- 

 tain tree of the Weft-Indies, and of the Aloe 

 under Experiment 5. plants will often imbibe 

 moifture in the night, as well in Stoves as 

 common Green-houfe, without fire; it is cer- 

 tainly of as great importance to the life of 

 the plants to difcharge that infected rancid 

 air, by the admittance of frefh, as it is to 

 defend them from the extreme cold of the 

 outward air, which will deftroy them, if let 

 in immediately upon them. It feems there- 

 fore to be a very reafonablc method which 

 fome ufe, viz. to cover fome of the inlets of 

 their Green-houfes on all fides with canvas, 

 and in extreme cold weather with fhutters 

 made of reed or ftraw, thro' which the air can 



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