_Effect of Direct Stimulus: Experiment 107._--The incipient contraction induced by direct stimulation is so great that the record obtained by the delicate method of balance cannot be kept within the plate. I, therefore, took the ordinary growth-curve on a moving plate. The first part of the curve represents normal growth; stimulus of feeble electric shock was applied at the highest point of the curve. This is seen (Fig. 104) to induce an immediate contraction and reversal of the curve which persisted for two and half minutes, after which growth was slowly renewed. The most interesting fact regarding the after-effect of stimulus is that the rate of growth became actually enhanced to three times the normal. This is clearly seen in the record (upper half of the figure) taken 20 minutes after stimulation, where the curve is far more erect than that of the normal rate of growth before stimulation. [Illustration: FIG. 104.--Variation of growth induced by direct stimulation. First part of the curve shows normal rate of growth. Direct stimulation induces contraction (reversal of curve). After-effect of stimulus seen in highly erect curve in upper part of record, taken 20 minutes after.] The effects of Indirect and Direct stimulation of the tendril are summarised below: (1) Indirect stimulation induces a sudden enhancement of rate of growth, followed by a recovery of the normal rate. (2) Direct stimulation induces a retardation of the rate of growth which may culminate into an actual contraction. _The after-effect of direct stimulus of moderate intensity is an enhancement of the rate of growth._ The experiments described above demonstrate the effects of direct and indirect electrical stimulus. I shall now proceed to show that mechanical stimulus induces effects which are similar to those of electric stimulus. EFFECTS OF DIRECT AND INDIRECT MECHANICAL STIMULUS. _Effect of Direct mechanical stimulus: Experiment 108._--In this case I took a tendril of _Cucurbita_, and attached it to the ordinary High Magnification Crescograph, the record of which gives the absolute rate of its normal growth, and the induced variation of that rate. The tendril was stimulated mechanically by simultaneous friction of its different sides. The immediate effect was a retardation of growth, the reduced rate being less than half the normal. There was a recovery on the cessation of the stimulus; the rate of growth was even slightly enhanced after an interval of 15 minutes. Table XXVI shows the immediate and after-effects of mechanical stimulation on growth. TABLE XXVI.--SHOWING THE IMMEDIATE AND AFTER-EFFECT OF MECHANICAL STIMULATION ON TENDRIL (_Cucurbita_).