THE GEOTROPIC CURVE 287 



suitable. Acceleration of the normal rate, with enhanced 

 steepness of curve, then indicates that the external agent 



Fig. ie»8. The complete geotropic curve (Crinum). 



co-operates with gravity ; depression of the rate with result- 

 ing flattening of the curve shows, on the other hand, the 

 antagonistic effect of the agent. 



Determination of Direction of Geotropic 



Stimulus 



The experiments which have been described show that 

 it is the upper side (on which the vertical lines of force of 

 gravity impinge) that undergoes excitation. The direction 

 of the incident stimulus must therefore be the vertical lines 

 of gravity. This conclusion is supported by the results 

 of three independent lines of inquiry : (i) the algebraical 



