Prof. Biiff on the Electricity of Plants. 123 



into contact with the parts of the plant whose electric deport- 

 ment was to be ascertained, the wires were connected with a 

 galvanometer, and the action upon the needle of the instrument 

 was observed. This procedure has, however, a source of error 

 connected with it from which the results of the observations 

 cannot be set free. It is well known, although not sufficiently 

 attended to by investigators of the electro-chemical school, that 

 platinum, in contact mth different liquids, exhibits different de- 

 grees of electric excitation. The sum or difference of these 

 actions must of necessity change the quantity, and perhaps also 

 the quality of the oi-iginal action due to the plant alone. The 

 observations communicated by Wartmanu and Becquerel, ewn 

 though of themselves perfectly correct, could therefore give no 

 answer to the question, whether plants, in their natural condi- 

 tion, and during their free growth, discharge electricity. 



To examine the electric deportment of a plant as it occurs in 

 nature, it is absolutely necessary to bring it into such relation 

 with the apparatus used in the experiments, that its natural 

 conditions shall be changed in the least degree possible. Now 

 the roots of thriving plants generally ramify themselves through 

 moist earth. The surface of their leaves, though they may not 

 be wet by rain or dew, are hygroscopically moist. It appeared 

 to me, therefore, necessary to establish the connexion of the 

 plants, or parts of plants, with the electrical apparatus, by means 

 of water alone. 



Upon this idea the following arrangement of the apparatus is 

 founded. Two glass beakers were filled with mercury to a height 

 of half an inch above the bottom, and then filled nearly to the 

 rim with water. Platinum mres, smelted into glass tubes, dipped 

 with their well-amalgamated ends, which projected for some 

 lines only beyond the glass tubes, into the mercury, their other 

 ends being connected with the helix of a very delicate multiply- 

 ing galvanometer. To complete this circuit, it was only necessary 

 to unite the water of both glasses by a conductor. When the 

 circuit was established by means of a strip of moist bibulous 

 pajMir, the needle continued motionless. A small addition of 

 common salt or of the acid sap of a plant to the one or the other 

 beaker, produced a deflection. By heating the water, or by mix- 

 ing the contents of both beakers well together, the equilibrium was 

 again established. A shaking of the fluid, which, when platinum 

 wir(!s are immersed in it, easily causes electrical excitation, was in 

 the present case without influence, inasmuch as the wii*es were pro- 

 tected by the glass tubes which surnjunded them from being un- 

 equally wetted. When an electric current was conducted through 

 the (;ircuit closed by the bibulous paj)er, the mercury surface be- 

 came indeed polarized, but much less so than platinum, and the 



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