CH. VIIl] MIMOSA, SLEEP. 223 



Melilotus, with its curious right and left-handedness 1 , of 

 Cassia, in which the leaves sink and twist, and of Des- 

 modium gyrans, in which the vertical droop of the larger 

 leaflets is particularly striking, should also be studied. 

 Movements not produced by means of a pulvinus, but by 

 the growth of the leaf-stalk should be examined; for 

 instance the nocturnal rise of the young leaves of Nico- 

 tiana glauca or of the cotyledons of the cabbage and 

 radish (Brassica oleracea and Raphanus sativus). 



In all these cases note that the nocturnal is more 

 nearly vertical than the diurnal position, and that when 

 there is close contact between neighbouring leaflets it is 

 generally the upper surface of the leaf that is protected. 



(256) Nyctitropic movements: Mimosa. 



In order to study the sleep movements of leaves more 



fe right 



FIG. 41. Exp. 256. 

 closely we employ a self-recording method. Fig. 41 is 



1 Power of Movement in Plants, p. 346, fig. 140. 



