THE EFFECT OF ELECTRICITY UPON PLANTS. 
201 
The excitatory effects of kathode and anode are antagonistic, but 
with a current flowing through the soil, there would always be a re- 
sultant excitation of the root, because the kathode effect is always 
greater than the effect due to the anode. ^ 
But in the case of overhead discharge with the wires overhead 
negative, the leaves and stem would on this view be more stimulated 
than the root, and the result should be a tendency to pump water 
downwards. On the whole then it is difficult, to make out a case for 
the rise of sap being aided by electric stimulation, and there is no ex- 
perimental demonstration of its occurrence in the plant. Bose would 
more probably attribute the effect of overhead discharge to direct 
stimulus of the growth responses in the plant. 
The acceleration of germination noted by so many observers, obviously 
involves some different factor, the only possible explanation seems to be 
that the current is used by the seed as a source of energy ; ^ this 
energy being directly used in anabolic process or in accelerating the 
katabolic processes of respiration. 
Pollacci ^ in a recent paper has suggested that the effect of a current 
passing through a green leaf may be to render carbohydrate synthesis 
possible from carbon dioxide and w^ater, even when the plant is in the 
dark. 
Bach ^ has suggested that the electrolysis of carbonic acid might 
result in the formation of formaldehyde in the neighbourhood of the 
kathode, but he advanced no experimental results in support of this view. 
Euler,^ as the result of practical investigation, found it impossible to 
obtain formaldehyde in this way. 
Waller® has detected the presence of small electromotive forces in 
a green leaf exposed to the light, but they are only found in a living 
tissue, and chloroplasts are necessary for their occurrence, no current 
being detected in a living petal exposed to the light. 
The experimental evidence that Pollacci brings forward is based 
chiefly upon the presence of starch in leaves kept in the dark with a 
current passing through them. Control leaves, also kept in the dark, 
contained no starch. 
Before we were aware of this work, Miss D. Johnson and I had 
investigated the same point, at first with results which seemed to con- 
firm those of Pollacci. 
^ Loc. cit., p. 560. 
Reynolds Green. Action of Light on Diastase. Phil. Trans. A^ol. 188, 
p. 188. 
^ Pollacci, G. Influenza dell’ electricita sulF assimilatione clorofilliana, 
Atti. 1st. Bot. Pabia II. 11; 7-10. 1905. 
* Bach. Sur la correlation entre la reduction par I’hydrogene naissant, 
I’electrolyse et la photolyse de I’acide carbonique. Comptes Rendus. Vol. 126, 
p. 479. 
® Euler. Berichte deut chem. Ges. Vol. .37, p. .3415. 1904. See also 
Meldola. Living Organism as a Chemical Agency. Trans, of the Chem. Soc. 
1906. Vol. 89, p. 758. 
® Waller. Electrical Eftects pf Light upon Green Leaves. Procs. of the 
Royal Soc. Vol. 67, p. 129. 1900. 
