I have described the action of stimulus on tissues in which, on account of sub-tonicity, growth has become enfeebled. I shall next take up the question of effect of stimulus on tissues in which growth, on account of extreme sub-tonicity, has been brought to a state of standstill.

SUMMARY.

The modifying influence of tonic condition on response is similar in pulvinated and growing organs.

The motile organ of Mimosa in a condition of sub-tonicity, exhibits a positive response, by expansion, increase of turgor, and erection of the leaf. Continuous stimulation converts the abnormal positive to normal negative.

In sub-tonic growing organs stimulus likewise induces a positive response, by expansion, increase of turgor and ac­cel­er­ation of the rate of growth. Continuous stimulation converts the abnormal ac­cel­er­ation to normal retardation.

Sub-minimal stimulus tends to induce even in normal tissues, an ac­cel­er­ation of rate of growth. Stimulus of moderate intensity induces in the same tissue the normal retardation of growth.

XIX.—RESUMPTION OF AUTONOMOUS PULSATION AND OF GROWTH UNDER STIMULUS

By