id="Page_026" class="x-ebookmaker-pageno" title="[Pg_026]"/>the movements in response to external stimuli, though apparently so diverse, could not be ultimately reduced to a fundamental unity of reaction. As a result of a very deep and penetrating study of the effects of various environmental stimuli, on different plant organs, he showed that the cells on two sides are unequally influenced, on account of different external conditions, and contract unequally, and hence the various movements are produced—that the many anomalous effects, hitherto ascribed to 'specific sensibilities,' are due to the 'differential sensibilities'—differential excitability of anisotropic structures and to the opposite effects of external and internal stimuli—that all varieties of plant movements are capable of a consistent mechanical explanation. Dr. Bose's "latest investigations recently communicated to the Royal Society have established the single fundamental reaction which underlies all these effects so extremely diverse."¹⁸

EXTENDED APPLICATION OF MECHANICAL THEORY

With an extended application of his mechanical theory, Dr. Bose has gradually removed the veil of obscurity from many a phenomenon in plant life. The 'autonomous' movements of plants, for example, which remained enveloped in mystery, received a satisfactory solution at his hands.

'AUTONOMOUS' MOVEMENTS

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.

It would not be out of place to mention that Dr. Bose, to carry on his researches on the Ascent of Sap, invented a new type of instrument (Shoshungraph). And for an accurate investigation on the phenomenon of growth of plants he devised an instrument (Growth Recorder) for instantaneous measurement of the rate of growth and another instrument (Balanced Crescograph) for determining the influences of various agencies on growth. So very marvellous these instruments that the growth, which takes place, during a few beats of pendulum, is measured, and, in less than a quarter of an hour, the action of fertilizers, foods, electrical currents and various stimulants are determined. "What is the tale of Aladdin and his wonderful lamp" exclaims the Editor of the Scientific American "compared with the true story told by the crescograph?... Instead of waiting a whole season, perhaps years, to discover whether or not it is wise to mix this or that fertilizer with the soil one can now find in a few minutes!" Yet these are the instruments which are better known in Washington than in Calcutta! The question of their application to practical agriculture has excited more interest in the United States of America than in this unfortunate land, which is an essentially agricultural country!

FUNDAMENTAL IDENTITY OF REACTIONS

Dr. Bose showed that there is no physiological response given by the most highly organised animal tissue that is not also to be met with in the plant. He carried on "Researches on Diurnal Sleep" and showed that the plant is not equally sensitive to an external stimulus during day and night, and that there is a fundamental identity of life-reaction in plant and animal, as seen in a similar periodic insensibility in both, corresponding to what we call sleep. He also showed that the passage of life in the plant, as in the animal, is marked by an unmistakable spasm. He invented, an instrument (Morograph) with which he recorded the critical point of death of a plant with great exactness. He demonstrated, in the most conclusive manner, that there is an essential unity of physiological effects of drugs on plant and animal tissues and showed the modifications which are introduced into these effects by the factor of individual 'constitution.' It may be mentioned casually that "this physiological identity in the effect of drugs is regarded by leading physicians as of great significance in the scientific advance of Medicine; since we have a means of testing the effect of drugs under conditions far simpler than those presented by the patient, far subtler too, as well as more humane than those of experiments on animals."¹⁹ Dr. Bose further demonstrated that there is conduction of the excitatory impulse in the plant, like the nervous impulse in the animal; and showed the possibility of detecting the wave in transit and measured the speed with which the excitation coursed through the plant and also showed that the velocity of excitation is modified, by different agencies, even in the case of ordinary plants. He also showed that the polar effects induced by electric currents, both in plants and animals, are identical.

These remarkable researches on Plant Response have 'revolutionised in some respects and very much extended in others our knowledge of the response of plants to stimulus.'

FURTHER DIFFICULTIES

Dr. Bose communicated his paper 'On the Electric Pulsation accompanying Automatic Movements in Desmodium Gyrans' to the Linnaean Society, which was published, in December 1902. Then, in 1903, he communicated to the Royal Society his researches on 'Investigation on Mechanical Response in Plants,' 'On Polar effects of Currents on the Stimulation of Plants,' 'On the Velocity of Transmission of Excitatory waves in Plants,' 'On the excitability and conductivity of Plant Tissues,' 'On the Propagation of the Electromotive Wave concomitant of Excitatory Waves in Plants,' 'On Multiple Response in