168 OUEEBNT ELBCTBICITT CHAP. XII. §. I. 



the Strong-scented leaves, such as the geranium, 

 &c. 



In judging of the results obtained by means of 

 these solutions °, we must consider their effect under 

 two points of view; l«t, as producing their own 

 chemical effect; and, 2ndly, as forming a better 

 conducting medium for the current. When the add 

 solution was employed, there can be no doubt that 

 the current then obtained was due to the immediate 

 action of the acid upon the tissue and juices of the 

 plant ; it always indicated its positive condition, and 

 with increased effect ; but how shall we account for 

 the action of the alkali? This should have indicated 

 a negative condition, if the current was due to its 

 own immediate action ; it was generally found, how- 

 ever, to indicate a positive state when in contact with 

 the cut surface of the petiole; and here I cannot 

 help believing but that it must have acted, under 

 these circumstances, as a conducting liquid. 



From these experiments we may deduce the follow- 

 ing conclusions : 



Is*, That when the electrodes of a galvanometer 

 are brought into contact, one with the surface of a 

 leaf, and the other with the sap flowing from the 

 same leaf, an effect occurs upon the needle, indi- 

 cating the surface of the leaf and the sap to be in 

 opposite electric states. 



" I heed scarcely point out the importance of paying particnlar 

 attention in the use of towels, and to cleanliness, especially of 

 the fingers and hands, when employing these solutions. 



