CH. VIIl] AVERRHOA. 2:^1 



a C-shaped piece of cardboard and graduate the inner 

 edge into 5\ i.e. make 36 graduations to the semicircle. 

 Now attach the card to a second stick fixed in the soil 

 so that the pulvinus is in the centre of the arc, and so 

 that the glass index can travel over the graduations. 

 The experiment is preferably conducted with illumination 

 from above, but even with a side light the movements 

 are clearly seen. 



The following table gives the readings in an experi- 

 ment of this sort : 



The leaf made 3 complete oscillations in 8 hrs. 23 m. 



(261) Autonomous movements : Averrhoa. 



If Averrhoa hilimbi is kept at a sufficiently high 

 temperature (e.g. 27° C), the movements of the leaflets 

 are easily seen. Each leaflet moves independently of the 

 rest, it falls suddenly from, e.g. 20' below the horizon to 

 40° below, and slowly rises in about 20 minutes to its 

 former position. If the temperature is increased to 

 31° — 32° C. the oscillations become more rapid and smaller 

 in amplitude, at the same time the mean position 

 of the leaflet falls to something like 50° below the 

 horizon instead of 30*^ as at flrst. These clianges are 



