The contradictory nature of the various responses is however not real; the apparent anomaly had lain in the fact that two definite fundamental reactions of opposite signs induced by stimulus had not hitherto been recognised and distinguished from each other. The innumerable variations in the resultant response are due to the summation of the effects of two fluctuating factors, with further complications arising from: (1) difference in the point of application of stimulus, (2) the differential excitability of the different sides of the responding organ, and (3) the effect of temperature in modifying tropic curvature. It is therefore most important to have the means for automatic record of _continuous_ change in the response brought about by various factors, which act sometimes in accord, and at other times in conflict. The autograph of the plant itself, giving a history of the change in response and its time-relations, is alone decisive in explanation of various difficulties in connection with plant movements, as against the various tentative theories that have been put forward. The analysis of the resulting effect, thus rendered possible, casts new light on the phenomena of response, proving that the anomalies which had so long perplexed us, are more apparent than real. One of the causes of uncertainty lay with the question, whether response changed with the mode of stimulation. I have, however, been able to show that _all forms of stimuli_ induce a definite excitatory reaction of contraction (p. 218). Tropic movements induced by unilateral action of stimulus may, broadly speaking, be divided into two classes depending on the point of application of stimulus: In the first, the point of application of unilateral stimulus is not on the responding organ itself, but at some distance from it. The question therefore relates to LONGITUDINAL TRANSMISSION of effect of stimulus. In the second, unilateral stimulus acts directly on the responding organ. For the determination of the resultant movement, it is necessary to take account of effects induced on the two sides of the organ. The side adjacent to the stimulus I shall designate as the _proximal_, and the diametrically opposite as the _distal_ side. The question to be investigated in this case relates to TRANSVERSE TRANSMISSION of effect of stimulus. It will be shown that the resulting movement depends on:-- (_a_) whether the tissue is a conductor or a non-conductor of excitation in a transverse direction, and (_b_) whether it is the proximal, or the distal side of the organ that is the more excitable.