Page:Collected Physical Papers.djvu/327

Rh a universal phenomenon characteristic of all plants and of all their different organs. My attempt was moreover directed in determining throughout the whole range of response phenomena a parallelism between the animal and the vegetable. That is to say, I desired to know, with regard to plants, what was the relation between the stimulus and response; what were the effects of superposition of stimuli; whether fatigue was present, and in what manner it affected the response; what were the effects of extremes of temperature; whether chemical reagents exercised any influence on the plant-response, as anæsthetics and poisonous drugs affected the responses of nerve and muscle.

The galvanometer used is a sensitive dead-beat D'Arsonval. A current 1/109 ampere gave a deflection of 1 mm. at a distance of 1 metre.

The Response Recorder.—In these response-curves the ordinate represents the intensity of E. M. variation, and