EFFECTS OF AIR ON LEAVES. tOl 



by conjecture, what .succeed iiig [)l)ilo,soj>lier8, 

 more eiilijilitened chemists, have ascertained. 

 His words arc remarkable : 



" We may therefore reasonably conclude, 

 that one great use of leaves is what has been 

 long suspected by many, viz. to perform in 

 some measure the same office for the support 

 of tlie vegetable life, that the lungs of ani- 

 mals do, for the support of the animal life ; 

 plants very probably drawing through their 

 leaves some part of their nourishment from 

 the air/' p. 326. A little further on he 

 adds, " And may not light also, by freely 

 entering the expanded surfaces of leaves and 

 flowers, contribute much to the ennobling the 

 principles of vegetables?" p. 328. 



Next in order of time to those of Hales 

 follow the experiments of Bonnet. We have 

 already detailed his observations on the 

 power of leaves to imbibe moisture ; whence 

 it is ascertained that plants are furnished with 

 a system of cuticular absorbents, which carry 

 fluids into their sap- vessels, so as to enable 

 them in some degree to dispense with sup- 

 plies from the root. With respect to the 

 effects of air upon leaves, this ingeniou.** 



