It was believed that automatically pulsating tissues draw their energy from a mysterious "vital force" working within. By controlling external forces, Dr. Bose stopped the pulsation and re-started it and thus demonstrated that the 'automatic action' was not due to any internal vital force. He pointed out that the external stimulus--instead of causing, as was customary to suppose, an explosive chemical change and an inevitable run-down of energy--brings about an accumulation of energy by the plant. And with the accumulation of absorbed energy, a point is reached when there is an overflow--the excess of energy bubbles over, as it were, and shows itself in 'spontaneous' movements. The stimulus being strong a single response--a single twitching of the leaflets--is not enough to express the whole of the leaf's responsive energy and it yields a multiple response--it reverberates--it manifests itself in 'automatic' pulsations. When, however, the accumulated energy is exhausted, then there is also an end of 'spontaneous movements.' There are strictly speaking, no 'spontaneous' movements; those known by that name are really due either to the immediate effects of external stimulus or to the stimulus previously absorbed and held latent in the plant to find subsequent expression--due to the direct or indirect action of external forces which are transformed in the machinery of the plants in obedience to the principle of the Conservation of Energy. "ASCENT OF SAP" "AND GROWTH" Dr. Bose then showed that, not gross mechanical movements alone, but also other invisible movements are initiated by the action of stimulus, and that the various activities, such as the "ascent of sap" and "growth" are in reality different reactions to the stimulating action of energy supplied by the environment. In this way, Dr. Bose showed that several obscure phenomena, in the life-processes of the plant, can be very satisfactorily explained by the Mechanical Theory.