I. On the causes and ecological significance of stomatal frequency, with special reference to the woodland flora

Abstract

Abstract Though numerous investigators have recorded observations on the number of stomata present in various species, comparatively little is known respecting the causes of their numerical variation. Studies on the “sun” and “shade” leaves of woodland plants brought to light the striking differences which the numerical frequency of stomata may exhibit in leaves of the same species when growing in different environments and even in different leaves of the same individual. Various hypotheses have been put forward to explain the larger number of stomata in sun-leaves. These will be considered later, but we may note here the apparent discrepancy with the observations of Ziegeler that the leaves of the more xerophytic Carices possess fewer stomata than the leaves of those species characteristic of damper habitats. Spitzer obtained similar results from an examination of the Grasses and Adamson appears to have arrived at a similar conclusion with regard to the various species of Veronica studied by him (“Comparative anatomy of the leaves of certain species of Veronica,” Veronica“ ‘Linn. Soc. Jour., Bot.,’ vol. XL, pp. 247-274, 1912).