CHAP. VII. SLEEP OF LEAVES. 333 



shown in Fig. 135. The temperature began to rise at 11.35 

 A.M. (in consequence of the -fire being lighted), but by 12.42 a 

 marked fall had occurred. It may be seen in the diagram that 

 when the temperature was highest there were rapid oscillations 



Fig. 134. 



Arerrhoa liUmbi: angular movements of leaflet during a change from 

 bright illumination to shade ; temperature (broken line) remaining 

 nearly the same. 



of small amplitude, the mean position of the leaflet being at the 

 time nearer the vertical. When the temperature began to fall, 

 the oscillations became slower and larger, and the mean position 

 of the leaf again approached the horizontal. The rate of oscil- 

 lation was sometimes quicker than is represented in the above 

 diagram. Thus, when the temperature was between 31 end 



