DIURNAL MOVEMENT OF DESMODIUM 



213 



closure was initiated at 5 p.m., when the hght was under- 

 going rapid diminution. The movement of closure was 

 completed at about 9 p.m. The leaflets remained closed 

 till 5 A.M. next morning, after which they began to open ; 

 this opening may commence even an hour earlier. It 

 should be borne in mind in this connection that since light 

 and rise of temperature are antagonistic in their reactions, 

 the effects of light and of fall of temperature would be con- 

 cordant, and the opening in the early hours may possibly 

 be hastened by the low temperature in the morning. The 

 leaflets were open to their utmost by 9 a.m., and they 

 remained open till the afternoon. 



Another interesting example of the diurnal movement 

 due to variation of light is found in the terminal leaflet of 

 Desmodium gyrans, an account of which is given below. 



Diurnal Movement of the Terminal Leaflet of 



Desmodium 



Both the petiole and the terminal leaflet of this plant 

 exhibit a very marked nyctitropic movement. In the 



Fig. 122. The day and night positions of the petiole and terminal 



leaflet of Desmodium gyrans. 



evening the petiole is raised and becomes almost erect, 

 while the terminal leaflet exhibits a sharp curvature 

 downwards (fig. 122). 



