Page:Life Movements in Plants.djvu/244

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

Electric response to Indirect stinmlus.—-—I have already explained how an identical reaction tinds diverse ex- pression in mechanical and electrical response, or in respon- sive variation of the rate. of growth. It is of interest in this connection to state that. my attention was first directed to the characteristic diti'erence between the etl'ects 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.

[ally/6N2an 85.—-—'l‘he records given in Fig. 80, exhibit

Flu. 80.--l".lct‘tric l't‘spt)ll:~c of .llusu ((1‘) Positive. (bl diphasit‘, (0) negative.

the electric response given by vegetahle tissues. On application of feeble stimulus at a distance from the responding point, the response “as by galvanometric positivity. Under