On a new method of estimating the aperture of stomata

Abstract

It is usually assumed that transpiration is regulated by two principal factors: (1) the relative humidity of the air, and (2) the degree of aperture of the stomata. Neither of these assumptions has been experimentally proved, though both of them are necessarily true, but it must be remembered that the factors referred to are not necessarily the only ones that govern the phenomena. The experiments hitherto made on (1) the effect of relative humidity are vitiated by want of precise knowledge as to the stomatal aperture during the course of the enquiry.