Chap. VII. SLEEP OF LEAVES. 383 



represented five ellipses, with their longer axes differently 

 directed. 



Albizzia lophantha (Tribe 23). — The leaflets at night come into 

 contact with one another, and are directed towards the apex of 

 the pinna. The pinnie approach one another, but remain in the 

 same plane as during the day ; and in this respect they differ 

 much from those of the above Sohrankia and Acacia. The main 

 petiole rises but little. The first-formed leaf above the coty- 

 ledons bore 11 leaflets on each side, and these slept like those 

 on the subsequently formed leaves ; but the petiole of this first 

 leaf was curved downwards during the day and at night 

 straightened itself, so that the chord of its arc then stood 16° 

 higher than in the day-time. 



Melaleuca ericcefolia (Myrtacese). — According to Bouche (' Bot. 

 Zeit.,' 1874, p. 359) the leaves sleep at night, in nearly the same 

 manner as those of certain species of Pimelia. 



CEnothera mollissima (Onagrariese). — According to Linnaeus 

 (' Somniis Plantarmn '), the leaves rise up vertically at night. 



Passifiora gracilis (Passifloracse). — The young leaves sleep by 

 their blades hanging vertically downwards, and the whole length 

 of the petiole then becomes somewhat curved downwards. 

 Externally no trace of a pulvinus can be seen. The petiole of 

 the uppermost leaf on a young shoot stood at 10.45 a.m. at 33° 

 above the horizon ; and at 10.30 p.m., when the blade was verti- 

 cally dependent, at only 15°, so the petiole had fallen 18°. That 

 of the next older leaf feU only 7°. From some unknown cause 

 the leaves do not always sleep properly. The stem of a plant, 

 which had stood for some time before a north-east window, was 

 secured to a stick at the base of a young leaf, the blade of 

 which was inclined at 40° below the horizon. From its position 

 the leaf had to be viewed obliquely, consequently the vertically 

 ascending and descending movements appeared when traced 

 oblique. On the first day (Oct. 12th) the leaf descended in a 

 zigzag line until late in the evening; and by 8.15 a.m. on the 

 13th had risen to nearly the same level as on the previous 

 morning. A new tracing was now begun (Fig. 161). The 

 leaf continued to rise until 8.50 a.m., then moved a little to the 

 right, and afterwards descended. Between 11 a.m. and 5 p.m. it 

 circumnutated, and after the latter hour the great nocturnal 

 fall commenced. At 7.15 p.m. it depended vertically. The 

 dotted line ought to have been prolonged much lower down in 

 the figure. By 6.50 a.m. on the following morning (14th) the 



