CHAP. VII. 



SLEEP OF LEAVES. 



351 



Fig. 142. 



Trifolium resupinatum. A plant left entirely free 

 before a north-east win- 

 dow, in such a position 

 that a terminal leaflet 

 projected at right angles 

 to the source of the light, 

 the sky being uniformly 

 clouded all day. The 

 movements of this leaflet 

 were traced during two 

 days, and on both wero 

 closely similar. Those 

 executed on the second 

 day are shown in Fig. 

 143. The obliquity of 

 the several lines is due 

 partly to the manner in 

 which the leaflet was- 

 viewed, and partly to its 

 having moved a little to- 

 wards the light. From 

 7.50 A.M. to 8.40 A.M. the 

 leaflet fell, that is, the 

 awakening movement was 

 continued. It then rose 

 and moved a little late- 

 rally towards the light. 

 At 12.30 it retrograded, 

 and at 2.30 resumed its 

 original course, having 

 thus completed a small 

 ellipse during the middle 

 of the day. In the even- 

 ing it rose rapidly, and 

 by 8 A.M. on the following 

 morning had returned to 

 exactly the same spot as 

 on the previous morning. 

 The line representing the 

 nocturnal course ought 

 to be extended much 

 higher up, and is here ;/ 

 abbreviated into a short. 



was placed 



