Page:An introduction to physiological and systematical botany (1st edition).djvu/231

 Rh by conjecture, what succeeding philosophers, more enlightened chemists, have ascertained. His words are 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 the vegetable life, that the lungs of animals 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 supplies from the root. With respect to the effects of air upon leaves, this ingenious