CHAr. VIL 



SLEEP OF LEAVES. 



369 



ciana OilUesii (botti belonging to Tribe 13), the leaves behave 

 in the same manner. 



Fig. 153. 



Hmmatoxylon Campechianum : A, branch during daytime ; B, branch with 

 leaves asleep, reduced to two-thirds of natural scale. 



Cassia (Tribe 14). — The nyctitropic movements of the leaves 

 in many species in this genus are closely alike, and are highly 

 complex. They were first briefly described by LinncBus, and since 

 by Dnchartre. Our observations were made chiefly on 0. flori- 

 hunda * and corymbosa, but several other species were casually 

 observed. The horizontally extended leaflets sink down verti- 

 cally at night; but not simply, as in so many other genera, for 

 each leaflet rotates on its awn axis, so that its lower surface 

 faces outwards. The upper surfaces of the opposite leaflets are 

 thus brought into contact with one another beneath the petiole, 

 and are well protected (Fig. 154). The rotation and other move- 

 ments are effected by means of a well-developed pulvinus at the 

 base of each leaflet, as could be plainly seen when a straight 

 narrow black line had been painted along it during the day. 

 The two terminal leaflets in the daytime include rather less than 

 a right angle : but their divergence increases greatly whilst they 



• I am informed by Mr. Dyer 

 that Mr. Bentliam believes that 

 C. floribundd (a common green- 

 house bush) is a liybrid raised in 

 France, and that it c'imes very 



near to C, Icevigatn. It is no doubt 

 the same as the form described by 

 lindley (' Bot. Eeg.,' Tab. 1422," 

 ftft C. Nerhertiana, 



