504 PLANT RESPONSE 



bud moving at a rate of "13 mm. per minute, ice-cold water 

 was applied on the upper surface, by means of a strip of 

 cloth, at the point marked in the figure by a downward 

 arrow (i) (fig. 210). In consequence of this the movement 

 is seen to be retarded, and in the course of five minutes it 

 came almost to a stop. The cloth was now removed, at the 



Fig. 210. Effect on Apogeotropic Movement of Application of Ice-cold 

 Water to Upper and Lower Surfaces alternately of a Horizontally laid 

 Crinum Lily 



The first part of the curve shows normal up movement, which is arrested 

 in consequence of the application of cold on the upper surface, at the 

 moment marked with a downward arrow {\). On removal of the 

 application at point marked ;' 4. , the normal apogeotropic movement is 



renewed, and continues unaffected by the application of cold below at 

 the moment marked with an upward arrow (t). 



moment marked in the curve, and the movement of response 

 to gravitation recommenced and tended gradually to attain 

 its original value, with the return of the upper surface to the 

 normal temperature. Ice-cold water was next applied on 

 the lower surface, at the moment marked by an upward 

 arrow (t), and it will be seen that this produced no percep- 

 tible effect on the rate of responsive curvature. A similar 



