I. On the electromotive properties of the leaf of dionæa in the excited and unexcited states

Abstract

The paper consists of five parts. Part I is occupied by the examination of two experimental researches, relating to the subject, which have been published in Germany since the date of the anthor’s first communication to the Royal Society in 1873, namely, that of Professor Munk on Dionæa, and of Dr. Kunkel on electromotive action in the living organs of plants. According to Dr. Munk, the electric properties of the leaf may be explained on the theory that each cylindrical cell of its parenchyma is an electromotor, of which the middle is, in the unexcited state, negative to the ends, and that on excitation the electromotive forces of the cells of the upper layer undergo diminution, those of the lower layer an increase. He accounts for the diphasic character of the electrical disturbance which follows mechanical excitation by attributing it to the opposite electromotive reactions of the two layers of cells. According to this theory, the cells resemble in their properties the “electromotive muscle-molecules” (“Unter-suchungen,” vol. i, p. 682, 1848, of du Bois Reymond) differing from them in so far that their poles are positive instead of being negative to their equatorial zones. Professor Munk has constructed a schematic leaf in which the cells are represented by zinc cylinders with copper zones. A schema so made is said by him to have the electromotive properties of the unexcited leaf. Dr. Kunkel’s experiments have for their purpose to show that all the electromotive phenomena of plants may be explained as consequences of the movement of water in the organs at the surfaces of which they manifest themselves.