82. Effect of electric stimulus on sub-tonic specimen of wheat seedling 221 83. Acceleration of growth under sub-minimal stimulus of light 224 84. Revival by stimulus of light of autonomous pulsations of _Desmodium gyrans_ at stand still 228 85. Renewal of growth in the mature style of a flower by the action of stimulus 229 86. Effect of light in diminution of amplitude and reduction of diastolic limit of pulsation of _Desmodium_ 236 87. Antagonistic effect of warmth in reduction of systolic limit 237 88. Contractile response of a growing bud of _Crinum_ 241 89. Response of _Mimosa_ pulvinus to white light 245 90. Response of _Mimosa_ pulvinus to blue light 246 91. Response of _Mimosa_ pulvinus to ultra-violet rays 247 92. Response of _Mimosa_ pulvinus to thermal radiation 248 I.--THE PROBLEM OF MOVEMENT IN PLANTS _By_ PROF. SIR J. C. BOSE. The phenomenon of movement in plants under the action of external stimuli presents innumerable difficulties and complications. The responding organs are very different: they may be the pulvini of the ‘sensitive’ or those of the less excitable leguminous plants; the petioles of leaves, which often act as pulvinoids; and organs of plants in a state of active growth. Taking first the case of the pulvinus of _Mimosa_, we find that it responds to mechanical stimulation, to constant electric current, to induction shock, to the action of chemical agents, to light, and to warmth as differentiated from thermal radiation. The reactions induced by these agents may be similar or dissimilar. An identical agent, again, may give rise to movements which are not merely different, but sometimes even of diametrically opposite characters. Certain organs, for example, direct themselves towards light, others away from it. Some plants close their leaflets on the approach of darkness, in the so-called position of ‘sleep’; apparently similar ‘sleep’ movement is induced in others by the action of the midday sun.