386 



Sir J. C. Bose and Mr. G. Das. 



or cathode will thus bring about appropriate curvatures. The galvano- 

 tropic effect may also be demonstrated by the pulvini of different plants such 

 as those of Erytlirina indica. One electrode is applied on one half of the 

 pulvinus, say the upper half, the second electrode being applied on the stem. 

 On making the pulvinus cathode, a curvature is produced, due to induced 

 contraction and concavity. Eeversing the current and making the pulvinus 

 anode causes an opposite curvature due to induced expansion and convexity. 

 An intensity of current above the critical here reverses expansion into con- 

 traction. 



Eo(ypt. 9. — For obtaining electrotropic response I took a growing bud of 

 Grinum, and applied two electrodes on one side of the organ in the growing 

 region. The electrodes were two pins thrust one above the other 1 cm. apart. 

 The effect of mechanical irritation was allowed to pass away. Application of 

 induction-shock of moderate intensity to one flank of the organ gave rise to a 

 positive curvature, the side directly excited becoming concave ; there was a 

 recovery after a period of rest. 



13. Thermonasty. 



In the well-known instance of the Crocus flower the effect of rise of tem- 

 perature is to bring about a relatively quicker rate of growth on one side of 

 the anisotropic organ. This causes the movement of opening ; fall of tem- 

 perature induces the reverse effect of closing. 



Expt. 10. — I give below records of the effect of rise and fall of tempera- 

 ture. Some specimens were found extraordinarily sensitive, and the follow- 

 ing records give the opposite reactions due to alternate introduction of puffs 

 of cold and warm air. The rise of temperature was so slight that a mercury 

 thermometer did not exhibit any change. Yet the effects of such slight 

 variation of temperature gave rise to marked responses of opposite signs. I 









c 



H 



R 



Fio. 11.— Thermonastic and radionastic responses of petal of Crocus. C, closing move- 

 ment due to cooling, and H, opening movement dud to warming ; E, closing 

 movement due to heat-radiation. Note opposite responses to thermal and radiation 

 action of heat. 



