

I 



^ 



f 



{* 



* 



/ 



*1 



%■ 



• ^ 



On Electricity in Plants^ and on Vegeto-lerrestrial Currents. 95 



The different electrical states of the earth and air have been 

 attributed also to the gradual decrease of terrestrial heat from the 

 lower parts of the solid crust, even to the highest limits of the 

 atmosphere. I have been the first to bring forward this opinion j 

 but as yet there is no fact that proves it. 



I proceed now to the concomitant electric effects obtained from 

 the earth and plants, after the plant is grown, or has made con- 

 siderable progress towards maturity. Operating with platinum 

 needles or pointed plates, as before, if one of the needles is in- 

 serted into the parenchyma of a stem or any branch of a plant 

 and the other in moist soil at some distance from the root (seve- 

 ral yards for example), there will always be a current, showing 

 that the earth contains an excess of positive electricity and the 

 parenchyma an excess of negativ^e. The deviation varies with 

 the humidity of the soil and the sappy state of the plant, but may 

 be 15, 20, 30, 40 degrees, or even more. 



The magnetic needle that deviates to 15 degrees, stops at 8 

 degrees after oscillating for a while; it still diminishes very 

 slowly to 2 or 3 degrees, owing to the polarity acquired by the 

 platinum; if this polarity is destroyed by moving the needle in 

 the ground without withdrawing it, the deviation increases 2 de- 

 ^ grees; while the same effect on the other needle restores the 



deviation to its first amount. This greater effect with the latter 

 is owing to the fact that as the sap in contact with the needle is 

 altering more or less rapidly, the current would have a new en- 

 ergy when the altered bed is disturbed by friction. There is 

 Kttle or no effect when one of the needles is in the wood or pith. 

 But if inserted in a number of leaves, while still on the branches, 

 me result is similar to that obtained from the parenchyma, prov- 

 ing a similar constitution for the sap of both. 



The same effects are obtained from all plants, even the herba- 

 ceous. ^ We may then receive as a principle, that in the act of 

 vegetation, when germination is accomplished, the ascending sap, 

 ^vhich communicates with the soil through the roots, carries up 

 an excess of positive electricity, whilst the parenchyma sap fur- 

 bishes to the air by aqueous evaporation an excess of negative 

 electricity. Vegetation therefore acts the reverse of the causes 

 yhich ordinarily render the air positive and earth negative. It 

 18 probable that the electric effects thus produced, as they are 

 iQcessant. should exert, especially in tropical regions and wooded 

 countries, considerable influence upon the electric state of the 

 atmosphere which plays so important a part in the production of 

 ^leteoric phenomena. 



-^s the cambium, or the substance so designated, is negative 

 compared with the wood and pith occupying the central part 

 ^f the plant, the positive state of the parenchyma as related to 

 ^he cambium, has only a secondary influence upon the effects 



r 



f\_ 



4 



I 



