ELECTRICITY. 
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vegetation has at present, like the whole subject, not been investigated scientifically. 
The destructive discharges of atmospheric electricity which are effected through 
trees by means of flashes of lightning ^ at least show that smaller differences of 
electrical equilibrium between the air and the earth may also be equalised by means 
of plants^. 
The researches on the action of the electric stimulus on the movements of 
protoplasm and of leaves the motion of which is caused by tension of the tissues 
have not at present led to any important result from a physiological point of 
view, although distinguished observers have paid attention to this subject. It can 
only be said in a general way that very weak constant currents or induction-shocks 
(for a short time) produce no perceptible effect ; that sufficiently strong electromotive 
force produces effects on the protoplasm and in the contractile tissues similar to 
those produced by a high temperature and by mechanical means ; and that finally, 
when the strength of the current is still further increased, the protoplasm is killed 
and the motility of the leaves permanently destroyed, but sometimes in the latter 
case without causing death. 
Jürgensen allowed the current from a battery of small Grove's elements, the force 
of which was regulated by a rheochord, to act under the microscope on the tissue of a 
leaf of ValUsneria spiralis. A constant current from one element produced no perceptible 
action; two or four elements caused a retardation of the protoplasmic movement, and 
when continued for a longer time completely stopped it. When the current was 
interrupted, the movement, if it had only been retarded, was restored to its original 
rapidity after the lapse of a short time ; if it had entirely ceased, it was not recom- 
menced even if the current was at once stopped. When the movement is thus arrested, 
acted as a conductor to electricity. In this way, by destroying the necessary electrical conditions, 
he thought forests tended to dissipate hail-clouds, Mem. de I'lnst. vol. XXXV. pp. 806, 807.] 
^ [The disruptive effect of lightning upon trees is probably due to the sudden conversion of 
moisture into steam. See Osborne Reynolds, Proc. Phil. Soc. Manch. 1874, P- ^S-] 
^ [Edwin Smith (Chemical News, Dec. 17, 1869) has detected constant currents of electricity 
passing in certain directions in plants, as follows : — In a cut piece of leaf-stalk (Rhubarb) from the 
end nearest the root to the end nearest the blade of the leaf ; from the outer side of the leaf-stalk 
nearest the cuticle to the inner axis ; from the lower end of the flower-stalk (Pseony) to the bract or 
petal ; from the upper to the under surface of the leaf; in the stem (Hawthorn) from the cambium to 
the outer cuticle ; in the root (several plants) from the outside to the axis, and from the root-stock 
towards the apex ; in the hollow stems of monocotyledonous plants (Grass) from the inner to the 
outer surface ; in the Potato from the centre to the outside ; but in the Lemon, Pear, Gooseberry, 
and Turnip from the outside to the centre ; in a living plant {Tropczohmi) from the plant itself to the 
soil. Kunkel {Joe. cit.) obtained similar results with the leaves and stems of a number of plants. He 
found that the direction of the current depended upon the relative moistness of the points in contact 
with the electrodes, any point being always positive with respect to another which is relatively dry. 
The currents which are observed appear therefore to be due to the travelling of water in the tissues. 
Phenomena of the same kind have been observed by Quincke in diaphragms. 
Dr. Burdon-Sanderson has made a remarkable series of observations on the electric currents in 
Dioncea muscipiila (see Report of British Association for 1873 ; also Nature, vols. VIII, X, and XV, 
and Proc. Roy. Soc. vol. XXI. p. 495). By the aid of Thomson's galvanometer he has shown that 
these currents are subject, in all respects in which they have been as yet investigated, to the same 
laws as those of animal muscle and nerve. Further, The Electrical Disturbance which accompanies 
the Excitation of the Stigma oi Mimulus luteus. Nature, XVI, 1879. See also Münk, Die elektrischen 
und Bewegungs-Erscheinungen am Blatte der Dioncea muscipula, Arch. f. Anat. u. Physiol. Du Bois- 
Reymond, 1876.] 
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