IX. Observations on stomata

Abstract

The most obvious method of investigating stomata is to examine them microscopically, and in this way a large number of researches into the conditions which open or close the stoma, and into the mechanism of the movements have been made. The majority of observers have either stripped off the epidermis or have cut surface sections. Neither method can be absolutely depended on as an index of the condition of the stomata in the uninjured leaf. Leitgeb and others have shown that the stomata in the periphery of such preparations are frequently more widely open than those in the centre—a fact which demonstrates the general untrustworthiness of the method. The stomata can only be well seen in stripped epidermis or thin surface sections, but such preparations are especially liable to the source of error above indicated. In spite of the difficulty of accurately observing the stomata in thick sections, and in spite of the general objections to this class of work, there is no doubt that much valuable work has been done in this way. It is, however, significant, as Stahl has pointed out, that Leitgeb (86) and Schellenberger (97) working in this manner have arrived at diametrically opposite results in determining the fundamental question whether or no the majority of terrestrial plants close their stomata at night.