INFLUENCE OF ELECTRICITY ON VEGETATION. 97 



of electricity of low tension in exciting the irritability of plants, 

 the movement of the stamens of the barberry, &c., were pub- 

 lished in 1812* by Nasse. The views of Du Petit Thenars on 

 the immediate connexion of electricity and vegetation were 

 supported by Gasc in 1813 ;t he, however, did not add any new 

 experimental evidence of much value. 



The subject of atmospheric electricity, one of the most im- 

 portant branches of the science, had attracted a great share of 

 the attention of electricians ever since the discoveries of Frank- 

 lin ; but although many observations have been recorded and 

 many experiments made, yet the theory of its source, even at the 

 present time, is very far from being complete. In 1825 M. 

 Pouillet read before the Academy of Sciences at Paris two ]Me- 

 moirs containing the results of his investigations into the sources 

 of atmospheric electricity. J This philosopher proved, that during 

 the germination of seeds a notable quantity of electricity is dis- 

 engaged. Setting aside all consideration of the more complicated 

 changes which take place during germination, we may consider 

 it as a mere process of oxidation, the whole effect produced on 

 germinating seeds by the air being the abstraction of a portion 

 of carbon and the formation of a quantity of carbonic acid gas ; a 

 change therefore analogous to the combustion of carbon, arifl con- 

 sequently one which we might expect, like that, would give rise 

 to the evolution of electricity. M. Pouillet's experiments though 

 delicate are very simple : he took twelve glass capsules, about 

 nine inches in diameter, well varnislied them with lac, and then 

 placed them in two rows, side by side, on a table covered witli the 

 same varnish ; they were then filled with vegetable earth, and 

 well connected by metallic wires with each otlier and with the 

 one plate of a condenser. Seeds having been sowed in the cap- 

 sules, the apparatus was examined from time to time ; for the first 

 two days no signs of electricity whatever were given by the gold- 

 leaf electrometer connected with the condenser, but on the third 

 day, when the plants began to appear above the surface of the 

 earth, the electrometer indicated negative electricity, and this 

 effect continued to be observed, night as well as day, for more 

 than a week. It is evident from this experiment that electricity 

 being set free during germination, the seeds become negative, 

 whilst the carbonic acid given off is, of course, positive — a very 

 important conclusion, if established ; both in respect to the source 

 of atmospheric electricity, and likewise as connected with the 



* Gilbert's Annalen der Physik, xli., p. 393. Goppert, Ann. des Sci. 

 Nat, XV., p. 72. 



f De rinfluence de I'Electricite dans la Fecondation. 

 X Annales de Chimie et de Physique, t. xxxv. p. 401 ; et t. xxxvi. p. 1. 

 VOL. I. H 



