1873.] Electrical Phenomena in the leaf of Dioneea muscipula. 495 



November 20, 1873. 



Sir GEORGE BIDDELL AIRY, K.C.B., President, in the Chair. 



In pursuance of the Statutes, notice of the ensuing Anniversary Meet- 

 ing was given from the Chair. 



Capt. John Herschel, R.E., elected in 1871, was admitted into the 

 Society. 



General Boileau, Mr. Etheridge, Mr. Merrifield, Mr. Newmarch, and 

 Prof. Ramsay, having been nominated by the President, were elected by 

 ballot Auditors of the Treasurer's Accounts on the part of the Society. 



The Presents received were laid on the Table, and thanks ordered for 

 them. 



The following communications were read : — 



I. " Note on the Electrical Phenomena which accompany irri- 

 tation of the leaf of Dioneea muscipula/ 3 By J. Burdon 

 Sanderson, M.D.j F.R.S., Professor of Practical Physiology 

 in University College. Received October 13, 1873. 



1. When the opposite ends of a living leaf of Dioneea are placed on non- 

 polarizable electrodes in metallic connexion with each other, and a 

 Thomson's reflecting galvanometer of high resistance is introduced 

 into the circuit thus formed, a deflection is observed which indicates the 

 existence of a current from the proximal to the distal end of the leaf. 

 This current I call the normal leaf-current. If, instead of the leaf, the 

 leaf-stalk is placed on the electrodes (the leaf remaining united to it) in 

 such a way that the extreme end of the stalk rests on one electrode and 

 a part of the stalk at a certain distance from the leaf on the other, a 

 current is indicated which is opposed to that in the leaf. This I call the 

 stalk-current. To demonstrate these two currents, it is not necessary to 

 expose any cut surface to the electrodes. 



2. In a leaf with the petiole attached, the strength of the current is 

 determined by the length of the petiole cut off with the leaf, in such a 

 way that the shorter the petiole the greater is the deflection. Thus in a 

 leaf with a petiole an inch long, I observed a deflection of 40. I then 

 cut off half, then half the remainder, and so on. After these successive 

 amputations, the deflections were respectively 50, 65, 90, 120. If in 

 this experiment, instead of completely severing the leaf at each time, it is 

 merely all but divided with a sharp knife, the cut surfaces remaining in 

 accurate apposition, the result is exactly the same as if the severance were 

 complete ; no further effect is obtained on separating the parts. 



3. Effect of constant current directed through the petiole on the leaf- 

 current. — If the leaf is placed on the galvanometer electrodes as before, 



VOL. xxi. 2 R 



