176 CDERENT ELECTHICirr CHAP. XTE. §. IV. 



of the apples, depending, however, upon the parts in 

 which the electrodes were placed. No definite effects 

 could he ohtained ; and as the effects might he re- 

 ferred to secondary actions, I do not think it neces- 

 sary to particularize the results. Becqueeel*, in 

 speaking of some similar results ohtained by Donne, 

 adds : " Les courants ne doivent pas gtre attribues 

 a la presence i'wa. acide et d'un alcali, mais hien 

 a I'heterogeneite des parties constituantes des fruits." 

 In the potato, carrot, and heet-root, similar effects 

 to those observed by Beoquekel were ohtained. In 

 radishes the external surface was positive to the centre. 



The following general conclusions may he de- 

 duced from the foregoing experiments : 



1st, That when the electrodes of a galvanometer 

 are brought into contact, one with the surface of the 

 leaf, and the . other with the sap flowing from the 

 same leaf, an effect occurs upon the needle indicating 

 the surface and the sap to be in opposite electric 

 states. These effects cannot be referred entirely to 

 ordinary electro-chemical actions, but may he re- 

 ferred, in part, to the organic changes which take 

 place in the leaf during vegetation. 



Und, When the electrodes are brought into contact, 

 one with the external surface of the spongioles of 

 a plant, and the other with the sap ascending from 

 the root, the sap and the external surface are in 

 opposite electric states. The effects which are here 

 " Traite de I'Eleotrioite, torn. iv. p. 164. 



