.f< 



1 



96 On Electricity in Plafits^ and on Vegeto-terrestrial Currents. 



just mentioned^ since the direction of the primitive current is not 

 affected by it. 



matters 



III. Are there direct Electric Currents in Plants. 



May we conclude from the facts presented in the first part of 

 this memoir that there are constant electric currents circulating in 

 plants and also between them and the earth? This question is 

 important to physiology, since such currents cannot circulate in 

 liquids without producing chemical action : and it is of no less 

 interest to the meteorologist. To reply to it, we must consider 

 whether the two conditions necessary for the production of such 

 currents are fulfilled. 



The first undoubtedly exists, as there are present two differ- 

 ent liquids reacting chemically upon one another through a me- 

 dium of permeable tissues : and it is the same with the second^ 

 which requires the contact of two liquids by insensible transition. 

 In fact, in a horizontal section of a stem of a plant, the immedi- 

 ate communication takes place readily through the tissues be- 

 tween the ascending sap and the parenchyma sap. In a longi- 

 tudinal section, it is well known that the ascending sap, before it 

 enters the plant by the roots, consists of water including some 

 air, carbonic acid gas, and small quantities of saline and organic 



taken up from the soil. In its passage, it dissolves by 

 degrees a portion of the substances met with along its course, 

 acquires increased density, and constitutes then the ascending 

 sap. The parenchyma sap, after elaboration in the leaves, loses 

 a portion of its constituent parts in the process of nutrition. 

 Each is in the condition necessary for mutual contact by insensi- 

 ble transition, and consequently for producing electric currents 

 without the addition of metallic plates. 



These currents ought to circulate as in the annexed figure. 

 VV is a longitudinal section of a plant ; ab 

 the bark ; cdy the cambium ; efthe wood ; 

 gh the pith. Positive electricity entering 

 at h and / through the roots, and ascend- 

 ing in the direction 6a, produces, as ap- 

 pears from the facts, partial currents pro- 

 ceeding from the bark to the pith, and this 

 even to the extreme branches. 



We are not able to make other induc- 

 tions from the facts thus far observed, nor 

 point out the chemical action resulting 

 from such currents in the tissues. Nevr 

 experiments are necessary before we can 1 

 on these points. 



