224 PHYSIOLOGY OF MUSCLES AND NERVES. 



years ago stated as the result of his observations, 

 that in the leaves of Venus' Flytrap {Dioncea musci- 

 pida), regular electric currents occur, which, during 

 the movement of these leaves, exhibit negative varia- 

 ation exactly as do nerve-currents. He was induced 

 to make his observations by Charles Darwin, who, in 

 the course of his study of insectivorous plants, at- 

 tempted to show an analogy between the leaf-move- 

 ments of the Dioncea and the muscular movements of 

 animals. Darwin's observations have since been pub- 

 lished in detail.! They show the interesting fact that 

 in various plants glandular organs occur which secrete 

 juices capable of digesting albuminous bodies. The 

 plant above mentioned, Dioncea muscipula, is provided 

 with these glands ; and in addition to this it is irri- 

 table, as is the Mimosa pudica described in the first 

 chapter. When an insect touches the leaf, the halves 

 of the leaf close on each other, and the imprisoned 

 insect is digested and absorbed by the secreted juice. 

 In judging of the nature of these leaf-movements, it is 

 necessary to decide whether they are really analogotis 

 to muscle-movements, and whether the identity extends 

 even to the electric phenomena, as Bm-don-Sanderson 

 w^ould have us beheve. Eecent researches by Professor 

 Munk of Berlin have not confirmed this. The move- 

 ments of the leaf of the Diono'a must be regarded as 

 entirely similar to those of the Mimosa pudica. These 

 movements are dependent, not on contractions, as are 

 those of muscle, but on curvatures which occur in the 

 leaf in consequence of an alteration in the supply of 

 moisture in the different cell-strata. The leaf does 

 indeed exercise electric action, though not in the simple 



' Oil Tnsecth'07'ou8 Plants. London, 1875. 



