^ mX 



Ji 



On Electricity/ in Plants^ and on Vegeto-terresirial Curi^ents. B5 



the other upon the skin which secretes an acid, the needle de- 

 viated fifteen to twenty or even thirty degrees, — the mucus of 

 the mouth on account of its alkaline nature giving the nega- 

 tive current. M. Donne obtained similar effects by experiment- 

 ing on the stomach and liver, one secreting an acid and the other 

 an alkali. Analogous effects take place with fruits; on inserting 

 a needle of platinum into the stem end of the fruit and another 

 into the opposite, there is an electric current; in apples and pears 

 the current is from the flower-end to the stem-end, and in peaches, 

 apricots and prunes, the reverse. If the needles are inserted at 

 opposite points, 90^=^ from the ends, (that is in the equatorial 

 plane,) there is no current. The effects obtained were evidently 

 due io^ the different composition of the liquids. On cutting a 

 prune in two equatorially, and then obtaining the juice from each, 

 and making with it a circuit, the currents were obtained as before, 



and in the same direction. The cause in such cases is evidently 



chemical. 



Similar results are obtained when experimenting in organized 

 bodies with two metallic conductors, if they are put in contact 

 With two different liquids separated by tissues or permeable mem- 

 branes. A frog prepared as by Galvani may be used in place of 

 nietallic conductors; its contractions indicate the electric effects 

 that are produced immediately when the circuit is formed. 



May the effects here manifested take place without the inter- 

 vention of metallic conductors or the frog? To this, I shall re- 

 ply soon. I mention here, that whenever two liquids react chem- 

 ically upon one another, if these liquids do not form part in a 

 closed circuit, there is an immediate recomposition of the two 

 electricities disengaged at the point of contact; but if one of the 

 two liquids is put in communication with the earth, or loses by 

 evaporation the electricity which it possesses, the electricity of the 

 ^ther liquid may be collected with the conductor. Such are the 

 data for studying the questions under consideration in this memoir* 



I. Electric effects produced by the Circulation of Sap. 



la plants, there is an ascending sap and also a cortical sap, the 

 latter differing in composition from the former, and having, ac* 

 cording to some physiologists, a descending movement. They 

 are separated by tissues and produce effects like those above men- 

 tioned. These effects are the more remarkable from their relation 

 to the composition of the bark and wood. To interpret them, it 

 js necessary briefly to recall what is known upon the nature and 

 disu^ibution of these two varieties o( sap. 



The stem of a ligneous dicotyledonous plant is formed of two 

 distinct parts, the bark, and the v^ood properly so called, separated 

 ^y a liquid substance considered by many physiologists a semi- 

 tl^id tissue, nallpfl rn^i>hinm whiVh i« thft nrincinal element of 



