Chap. VII. SLEEP OF LEAVES. 331 



midrib. This filament acted as an index; and as tlie leaf rose 

 and fell, rotating about its basal joint, its angular movement 



Fig. 133. 



Aveirhaa bilimhi: angular movements of a leaflet during its erening 

 descent, when going to sleep. Temp. 78°-81° F. 



could be recorded by reading off at short intervals of time the 

 position of the glass filament on the graduated arc. In order 



