Chap. VII. SLEEP OF LEAVES. 355 



sommet, les inferieures vers la base du petiole commiui ; " but 

 the leaflets on a young plant observed by us in the green- 

 house merely sank vertically downwards at night. The leaflets 

 are raised in Sphmropliysa salsola, Oolutea arborea, and Aslra- 

 galus uUyinosus, but are depressed, according to Linnajus, in 

 Olycyrrhiza. The leaflets of Edbinia ps.udv-acacia likewise sink 

 vertically down at night, but the petioles rise a little, viz., in 

 one case 3°, and in another 4°. The circumnutating move- 

 ments of a terminal leaflet on a rather old leaf were traced 

 during two days, and were simple. The leaflet fell slowly, in a 

 slightly zigzag line, from 8 a.m. to 5 p.m., and then more 

 rapidly; by 7 a.m. on the following morning it had risen to its 

 diurnal position. There was only one peculiarity in the move- 

 ment, namely, that on both days there was a distinct though 

 small oscillation up and down between 8.30 and 10 a.m., and 

 this would probably have been more strongly pronounced if 

 the leaf had been younger. 



Coronllla rosea (Tribe 6). — The leaves bear 9 or 10 pairs ol 

 opposite leaflets, which during the day stand horizontally, with 



Fig. 146. 



CoroniUa rosea : leaf aaleep. 



their midribs at right angles to the petiole. At night they rise 

 up, so that the opposite leaflets come nearly into contact, and 

 those on the younger leaves into close contact. At 'the same 

 time they bend back towards the base of the petiole, until their 

 midribs form with it angles of from 40° to 50° in a vertical 

 plane, as here figured (Fig. 146). The leaflets, however, some- 

 times bend so much back that their midribs become parallel to 

 Bnd lie on the petiole. They thus occupy a reversed position 

 to what they do in several Leguminosse, for instance, in Mimosa 



