FUNCTION IN PLANT LIFE 7 



(7) Plants grown in pots or removed from the earth 



and placed in other receptacles differ materially 

 in their electrical constitution from those grown 

 in the earth. 



(8) If a suitable electrolyte, other than water, is 



mixed with the soil it is possible to grow plants 

 with much less moisture, and 



(9) Growth may be stimulated by means of a con- 



tinuous current of electricity of low potential and 

 proper sign. 



In the experiments of which an account is about to be 

 given the recording instrument was a Kelvin Astatic 

 Reflecting Galvanometer (see p. 235) of 80,000 ohms 

 resistance at 15 C., and a sensibility of about 4,000 divisions 

 of the scale, at a metre distance, per micro-ampere. My 

 chief difficulty was in the selection of a reliable form of 

 electrode. Those of the non-polarisable variety were, for 

 reasons into which I need not presently enter, deemed 

 unsuitable. Needles were obviously necessary. Platinum 

 was shown by Oliver Heaviside in 1885 * to set up secon- 

 dary action even in distilled water, and most amalgams 

 were open to the same objection as well as to the suspicion 

 of want of homogeneity. Finally, steel was chosen as the 

 metal, and the electrodes with which more than ten 

 thousand tests were taken without there being one dis- 

 cordant result were darning-needles of equal gauge con- 

 nected to flexible wires of low resistance. That there are 

 theoretical objections to this form of electrode I am well 

 aware, but, as I propose to prove, they cannot be upheld 

 in face of the evidence to be adduced. 



In normal conditions of weather and in countries free 

 from frequent seismic and magnetic disturbances, the 

 Earth is always the negative and the Air the positive 

 terminal of Nature's electrical system. 



* The Electrician. 



