[Book Reviews]

Abstract

THIS paper contains an interesting contribution to the question of the course taken by the sap of vascular plants on its way from the roots to the leaves. The view taken by Sachs, that the current passes through the substance of the lignified cell-walls, has, as is well known, been disputed by Böhm, Elfving, and many others, who maintain that it ascends through the cavities of the vessels and tracheides. Various observers have endeavoured to bring the question to an experimental decision by stopping up,in one way or another, the cavities of the water-conducting elements, and then observing whether the current is interrupted. Sachs and Dufour endeavoured to attain this result by sharply bending the stems of actively-transpiring plants, but this method is obviously unsatisfactory, owing to the difficulty of proving that the cavities are completely closed. Elfving attacked the problem in a different way. He injected portions of the stem of woody plants with cocoa-butter, melted at a temperature of 30° C., and satisfled himself that the cavities were really filled up when the injected material had solidified. Under these conditions he found that a pressure of 60 cm. of mercury failed to force any water through the wood, though before the injection I cm. of water had sufficed to cause filtration.

Une Expérience sur l'Ascension de la Sève chez les Plantes.

Par Léo Errera, Professeur à l'Université de Bruxelles. Comptes rendus de la Société Royale de Botanique de Belgique, tom. xxv. 2ième partie, 1886.