Abstract

Abstract Many species of Mimosa are distinguished by the rapidity with which they conduct excitation, as shown by the successive fall of their leaves and closure of the leaflets after stimulation. Recently great progress has been made in the study of this conduction through the experimental work carried out by Dr. U. Ricca, at Genoa, mainly on M. Spegazzinii (1 and 2). It had been discovered so long ago as 1824 by Dutrochet (quoted in Ricca, 1, p. 59) that in M. pudica, the best-known species, excitation can be conducted through a zone of stem from which the tissues outside the wood have been removed all round ; and this result, though at one time doubted, has since been repeatedly confirmed. It was also found by McDougall (3) that excitation can pass a zone of stem that has been completely killed by hot water. Thus, it already seemed probable that, in the stem at least of M. pudica, conduction must take place by the wood, and not by the phloem, as maintained by Haberlandt (4).