XV.—EFFECT OF MECHANICAL STIMULUS ON GROWTH

By

Sir J. C. Bose.

Amongst the various stimuli which induce excitation in Mimosa may be mentioned the irritation caused by rough contact, by prick, or wound. Friction causes moderate stimulation, from which the excited pulvinus recovers within a short time. But a prick or a cut induces a far more intense and persistent excitation; the recovery becomes protracted, and the wounded pulvinus remains contracted for a long period.

I shall now describe the effect of mechanical irritation on growth. For moderate stimulus, I employ rough contact or friction; more intense stimulation is caused by a prick or a cut.

EFFECT OF MECHANICAL IRRITATION.

Fig. 74.—(a) N, normal rate of growth; F, re­tard­ed rate im­me­di­ate­ly after fric­tion; A, partial re­cov­ery after 15 minutes.

(b) N, normal; W, immediately after wound; C, an hour after.