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LIFE MOVEMENTS IN PLANTS

brought about a diphasic response, positive followed by negative. Direct stimulus gave rise only to a negative response.

Electric response to Indirect stimulus.—I have already explained how an identical reaction finds diverse expression in mechanical and electrical response, or in responsive variation of the rate of growth. It is of interest in this connection to state that my attention was first directed to the characteristic difference between the effects of Direct and Indirect stimulus from the study of electric response of vegetable tissues. I found that while Direct stimulus induced negative electric response, Indirect stimulus gave rise to a positive response. The clue thus obtained led to the discovery of positive mechanical response under Indirect stimulus.

Experiment 85.—The records given in Fig. 80, exhibit
Fig. 80.—Electric response of Musa (a) Positive, (b) diphasic, (c) negative. the electric response given by vegetable tissues. On application of feeble stimulus at a distance from the responding point, the response was by galvanometric positivity. Under

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