206 MIMOSA, SLEEP. [CH. VIII 



revolving drum used for auxanometer experiments. The 

 tracing only records changes in the vertical position of 

 the free end of the petiole, and does not give the angle 

 which the petiole makes with the horizon, but if a few 

 readings of the angle are taken, the rest can be calculated 

 from the known length of the petiole and writer. It will 

 suffice for our present purpose to know that at 7 p.m. the 

 petiole was roughly 45° below, and at 4 a.m. 60° above 

 the horizon. 



Fia. 40. Exp. 256. 



The tracing shows that the leaf sank with increasing 

 and then decreasing rapidity from 4 p.m. to 7 p.m., when 

 it rose (at first slowly) until 3 a.m. It then remained 

 stationary until 4.30, when a fall again occurred, followed 

 by irregular movements continuing to noon. 



(257) Paraheliotropism : Averrhoa bilimbi. 



The leaves of many plants assume in bright sunshine 

 a more or less vertical position, which has been sometimes 



