I shall in a subsequent paper formulate a generalised Law of Effects of Direct and Indirect Stimulus. From the experiments already described it is seen that: _Direct stimulus induces negative variation of turgor, contraction, fall of leaf of_ Mimosa, _electric change of galvanometric negativity, and retardation of the rate of growth._ _Indirect stimulus induces positive variation of turgor, expansion, erection of leaf of_ Mimosa, _electrical change of galvanometric positivity, and acceleration of the rate of growth._ It is seen that Indirect stimulus gives rise to dual reactions, seen in positive and negative responses; of these the negative is the more intense. When the intervening distance is reduced, the resulting response becomes negative; this is due not to the absence of the positive, but to its being masked by the predominant negative. From the principle of continuity, this will also hold good in the limiting case, where by the reduction of the intervening distance to zero, the stimulus becomes Direct. In other words, Direct stimulus should also give rise to both positive and negative reactions. Of these the positive is masked by the predominant negative. So much for theory; is it possible to unmask the contained positive in the resulting negative response under Direct stimulus? This important aspect of the subject will be dealt with in the following Paper. SUMMARY. The application of Direct stimulus gives rise to an electric response of galvanometric negativity. The application of stimulus at a distance from the responding point, _i.e._, Indirect stimulus, gives rise to positive electric response. The mechanical responses of sensitive plants also exhibit similar effects, _i.e._, a negative response under Direct, and positive response under Indirect stimulus. In the responsive variation of growth, Direct stimulus induces a retardation, and Indirect stimulus an acceleration of the rate of growth. The effects of Direct and Indirect stimulus on vegetable organs in general are as follows: Direct stimulus induces negative variation of turgor, contraction, fall of leaf of _Mimosa_, electric change of galvanometric negativity, and retardation of the rate of growth. Indirect stimulus induces positive variation of turgor, expansion, erection of leaf of _Mimosa_, electrical change of galvanometric positivity and acceleration of the rate of growth. XVIII.--RESPONSE OF GROWING ORGANS IN STATE OF SUB-TONICITY _By_ SIR J. C. BOSE. The normal response of a growing organ to Direct stimulus is _negative_, that is to say, a retardation of the rate of growth. This is the case under forms of stimuli as diverse as those of mechanical and electric shocks, and of the stimulus of light. ABNORMAL ACCELERATION OF GROWTH UNDER STIMULUS.