VI COMPARATIVE ELECTRO-PHYSIOLOGY 



employed was mechanical and quantitative, thus obviating 

 many sources of complication. By this method I was able 

 to show that every plant, and every organ of every plant, gave 

 true excitatory electrical response. As observations similar 

 to these were subsequently made by another investigator, 

 I quote here the following summary of my results from the 

 preliminary account which I communicated to the Royal 

 Society, May 7, and afterwards read, with accompanying ex- 

 perimental demonstration, before the Society, on June 6, 1901. 



' An interesting link, between the response given by inor- 

 ganic substances and the animal tissues, is that given by plant 

 tissues. By methods somewhat resembling that described 

 above, I have obtained from plants a strong electric response 

 to mechanical stimulus. The response is not confined to 

 sensitive plants like Mimosa, but is universally present. I 

 have, for example, obtained such response from the roots, 

 stems, and leaves of, among others, horse-chestnut, vine, 

 white lily, rhubarb, and horse-radish. The " current of 

 injury " is, generally speaking, from the injured to the 

 uninjured part. A " negative variation " is also produced. I 

 obtained both the single electric twitches and tetanus. Very 

 interesting also are the effects of fatigue, of temperature, of 

 stimulants, and of poison. Definite areas killed by poison 

 exhibit no response, whereas neighbouring unaffected portions 

 show the normal response.' 1 



It may be well to point out here that at the time when this 

 communication was made, the view that ordinary plants 

 were excitable, and responded to mechanical stimulus by 



1 A more complete account will be found in the report of my 'Friday 

 Evening Discourse ' before the Royal Institution, May 10, 1901, and in the 

 Journal of the Linnean Society, vol. xxxv. p. 275. 



