382 LIFE MOVEMENTS IN PLANTS 



was no neutralisation or reversal, demonstrating the absence 

 of transverse conduction (c/. Fig. 132). 



Fig. 141. — Positive para-heliotropic response of leaflets of Eryihrina indica. 



Para-heliotro2nc movement of leaflets of Mimosa pudica : 

 Experiment 148. — These leaflets, as previously stated, fold 

 themselves upwards, when strongly illuminated either from 

 above or below. Diffuse electric stimulation also induce a 

 closing movement upwards ; hence the upper half of the 

 pulvinule of these leaflets are the more excitable. In order 

 to obtain a continuous record of the leaflet under the 

 action of unilateral light, I constructed a very delicate 

 recording lever magnifying about 150 times. Light of 

 moderate intensity from a 100 candle-power incandescent 

 lamp was applied on the less excitable lower side of the 

 pulvinule. The record (Fig. 142) shows that the imme- 

 diate response is positive, or a movement towards the light. 

 But owing to transverse conduction, through the thin and 

 highly conducting pulvinule, the response was quickly 

 reversed into a very pronounced negative, or movement 

 away from light. Had a delicate means of obtaining 

 magnified record not been available, the slight positive 

 twitch, and the gradual transition from positive to nega- 

 tive phototropic curvature would have passed unnoticed. 

 Application of light from above gave, on account of the 

 greater excitability of the upper half of the pulvinule, a 

 pronounced positive response or movement towards light. 

 The anomaly of an identical organ appearing as positively 

 heliotropic when acted by light from above, and negatively 



