XIV—EFFEC’T OF ELECTRIC STIMULUS ON GROWTH
By
Sir J. C. Bose,
Assisted by
GURUPRASANNA DAS.
In plant physiology, the word ‘stimulus’ is often used in a very indefinite manner. This is probably due to the different meanings which have been attached to the word. An agent is said to stimulate growth, when it induces an acceleration. But the normal ell'ect of stimulus is to zausc a retardation of growrh. It is probably on amount of lack of precision in the use of the term that we often find it stated, that a stimulus sometimes accelerates, and at other times, retards growth. In order to avoid any ambiguity, it is very desirable that the term stimulus should always be used in the. sense as definite as in animal physiology. Au induction shock, a condenser dis- charge, the make or break of a constant current, a sudden variation of tempe'ature, and a mechanical shock bring about an excitatory contraction in a muscle. These various forms of stimuli cause, as we have. seen, a similar excitatory contraction of the motile pulvinus of Mimosa, lnuh't'a. We shill enquire whether the diverse forms of stimuli enumerated above, exert similar or dill'orent reactions on the growing organ.
EFFECT OF ELECTRIC STIMULUS OF VARYING INTENSITY AND DURATION.
The form of stimulus which is extensively used in physiological investigations, is the electric stimulus of
