Excerpt from Physiological Researches, Vol. 1: July, 1913 August, 1916 The experiments described in this paper had as their chief purpose to discover (a) whether the water content of a given soil at the time when plants growing therein become permanently wilted remains a constant when wilting occurs under widely varying environmental conditions, and can therefore be determined with accuracy by calculation from the known physical constants of the soil, and (b) whether there is a definite and constant relation between the water content of the plant and that of the soil at the time of wilting, under such varying conditions. The work was performed at the Desert Laboratory of the Carnegie Institution, at Tucson, Arizona, during the summer of 1911. The plants used were Zea mays L., Phaseolus vulgaris L., Xanthium commune Britton, Martynia louisiana Mill., and Physalis angulata var. Linkiana Gray. The chief results follow: 1. For large numbers of turgid individuals of the same age and species, the average water content of all the normal functioning leaves is approximately a constant under the midsummer conditions of southern Arizona. Departures of individual plants from the average normal foliar water content for the species were few and small in the five species studied. 2. Plants beginning to lose turgor in the youngest leaves show an average foliar water content which is fairly constant for the species and which bears a definite ratio to the average normal water content for turgid individuals of that species. 3. Temporary wilting of the younger foliage is of frequent occurrence and is conditional only upon a temporary, but more or less prolonged, maintenance of the rate of transpiration at a magnitude in excess of the rate of absorption for the same period; hence, this form of wilting is not related merely to the moisture content of the soil, but also to aerial conditions, especially to the evaporating power of the air and to the intensity of solar insolation. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.