310 PKESENT STATE OF ORGANIC ELECTRICITY, 



plant and soil The electrical effects observed by M. Pouillet, 

 in this first period of vegetation, correspond with the ordinary 

 electrical conditions of the earth and atmosphere. 



But according to M. Becquerel's own observations,* the 

 electrical relations of the plant to the soil and air are reversed 

 after germination is completed. If the electrodes of the gal- 

 vanometer are inserted the one into the stem or branch, or 

 passed through a number of leaves laid together, but still 

 adherent, the other into the soil the former will exhibit an 

 excess of negative, the latter of positive electricity, in propor- 

 tion to the humidity of the soil and the succulence of the 

 plant. 



It may, therefore, be presumed that in the act of vegetation, 

 after germination is accomplished, the ascending sap, which 

 communicates by means of the root with the soil, conveys to 

 it continuously the excess of positive electricity which it has 

 acquired during its course upwards in its reactions more par- 

 ticularly with the descending sap ; while the latter furnishes 

 to the air, by exhalation, its excess of negative electricity. 



Vegetation, therefore, produces electric effects contrary to 

 those which render the air and soil respectively positive and 

 negative. 



Longitudinal Electrical Currents in the Dicotyledonous Plant. 

 Becquerel states t that if the electrodes of the galvanometer 

 be inserted transversely into the parenchyma of the bark, the 

 one a certain distance above the other, or if one be inserted 

 between the bark and wood, and the other be passed through 

 a number of leaves, superimposed and still adherent, the 

 needle will indicate a current passing from below up wards J 



* Mem. de I'Acad. des Sciences, torn, xxiii. pp. 61, 62. 



t Ibid., torn, xxiii. pp. 55, 56. 



J The statement of the direction of an electrical current is a conventional 

 form of expression, which ought to convey merely an indication of the relative 

 positions of its positive and negative extremities, and consequently of the two 

 polar forces, both of which exist in the current. In the circuit formed by the 



