INFLUENCE OF ELECTRICITY ON VEGETATION. 91 



jar. Four of these jars were prepared, the same number of seeds 

 being placed in each, and care being taken that they were all 

 exposed to exactly the same circumstances, only that two were 

 kept constantly electrified by connexion with the positive con- 

 ductor of a powerful machine, whilst the other two were un- 

 touched ; the seeds all came up alike, and there was no difference 

 in the time of germination or in the size of the young plants. 

 The same result was obtained on repeating the experiment, two 

 being positively and two negatively electrified. Other seeds 

 being placed on cork floating on water, and directly connected 

 with the positive or negative conductor of the machine, ger- 

 minated as under ordinary circumstances. These experiments 

 were varied in several different ways, the same effect, however, 

 being always obtained ; and hence M. Schwankhardt became 

 convinced of the truth of Dr. Ingenhousz' observations, and 

 agreed with him in believing that though it might probably exert 

 some influence on growing plants, yet it was unjust to conclude 

 that the effects described by previous electricians were due to its 

 agency. They repeated many of these experiments exactly, with 

 cress seeds and various bulbs, and obtained such conflicting and 

 uncertain results that they could not come to any definite con- 

 clusions. Amongst others, they carefully repeated M. Comus's 

 experiment on the sensitive plant, described by Bertholon,* 

 and satisfied themselves that the effects produced were purely 

 mechanical, in which they were borne out by the Count de 

 Caleppi and Professor Landriani of Milan, though the latter 

 still continued to hold the old views respecting the great in- 

 fluence of electricity on vegetation. f 



This paper of Schwankhardt was opposed by Dr. Duvarnier,| 

 who, without adding any new facts, contented himself with throw- 

 ing out doubts as to the accuracy of the experiments of In- 

 genhousz and Schvi'ankhardt, referring at the same time to the 

 numerous experiments of other electricians. Dr. Ingenhousz also 

 published some observations on the subject, § in which he confirms 

 the statements of Schwankhardt, repeats his own doubts of the 

 accuracy of previous experiments, and states his belief that the 

 effects observed by former electricians were due to the agency of 

 light, and not of electricity. He describes experiments, in which 

 seeds, placed on the bottom of Leyden jars sixteen inches high 

 and seven and a-half in diameter, and compared with similar 

 seeds equally shaded from the light, but not electrified, showed 

 no superiority of growth whatever. These experiments, how- 



* Bertholon, Electricite des Ve'getaux, p. 264. 



t Ingenhousz, Expe'riences sur les Vegetaux, ii. p. 264. 



I Rozier, 1786, i. p. 98. § Ibid., 1786, i. 81. 



