Acacia Farnesiana (Tribe 22).—­The different appearance presented by a bush of this plant when asleep and awake is wonderful.  The same leaf in the two states is shown in the following figure (Fig. 160).  The leaflets move towards the apex of the pinna and become imbricated, and the pinnae then look like bits of dangling string.  The following remarks and measurements [page 382] do not fully apply to the small leaf here figured.  The pinnae move forwards and at the same time sink downwards, whilst the main petiole rises considerably.  With respect to the degree of movement:  the two terminal pinnae of one specimen formed together an angle of 100o during the day, and at night of only 38o, so each had moved 31o forwards.  The penultimate pinnae during the day formed together an angle of 180o, that is, they stood in a straight line opposite one another, and at night each had moved 65o forwards.  The basal pair of pinnae were directed

Fig. 160.  Acacia Farnesiana:  A, leaf during the day; B, the same leaf at night.

during the day, each about 21o backwards, and at night 38o forwards, so each had moved 59o forwards.  But the pinnae at the same time sink greatly, and sometimes hang almost perpendicularly downwards.  The main petiole, on the other hand, rises much:  by 8.30 P.M. one stood 34o higher than at noon, and by 6.40 A.M. on the following morning it was still higher by 10o; shortly after this hour the diurnal sinking movement commenced.  The course of a nearly full-grown leaf was traced during 14 h.; it was strongly zigzag, and apparently [page 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 pinnae 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 Schrankia and Acacia.  The main petiole rises but little.  The first-formed leaf above the cotyledons 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 16o higher than in the day-time.

Melaleuca ericaefolia (Myrtaceae).—­According to Bouché (’Bot.  Zeit.,’ 1874, p. 359) the leaves sleep at night, in nearly the same manner as those of certain species of Pimelia.

Oenothera mollissima (Onagrarieae).—­According to Linnaeus (’Somnus Plantarum’), the leaves rise up vertically at night.