Hedysarum coronarium (Tribe 6).—­The small lateral leaflets on plants growing out of doors rose up vertically at night, but the large terminal one became only moderately inclined.  The petioles apparently did not rise at all.

Smithia Pfundii (Tribe 6).—­The leaflets rise up vertically, and the main petiole also rises considerably.

Arachis hypogoea (Tribe 6).—­The shape of a leaf, with its two pairs of leaflets, is shown at A (Fig. 147); and a leaf asleep,

Fig. 147.  Arachis hypogoea:  A, leaf during the day, seen from vertically above; B, leaf asleep, seen laterally, copied from a photograph.  Figures much reduced.

traced from a photograph (made by the aid of aluminium light), is given at B. The two terminal leaflets twist round at night until their blades stand vertically, and approach each other until they meet, at the same time moving a little upwards and backwards.  The two lateral leaflets meet each other in this same manner, but move to a greater extent forwards, that is, in a contrary direction to the two terminal leaflets, which they partially embrace.  Thus all four leaflets form together a single packet, with their edges directed to the zenith, and with their lower surfaces turned outwards.  On a plant which was not growing vigorously the closed leaflets seemed too heavy for the [page 357] petioles to support them in a vertical position, so that each night the main petiole became twisted, and all the packets were extended horizontally, with the lower surfaces of the leaflets on one side directed to the zenith in a most anomalous manner.  This fact is mentioned solely as a caution, as it surprised us greatly, until we discovered that it was an anomaly.  The petioles are inclined upwards during the day, but sink at night, so as to stand at about right angles with the stem.  The amount of sinking was measured only on one occasion, and found to be 39o.  A petiole was secured to a stick at the base of the two terminal leaflets, and the circumnutating movement of one of these leaflets was traced from 6.40 A.M. to 10.40 P.M., the plant being illuminated from above.  The temperature was 17o — 17 1/2o C., and therefore rather too low.  During the 16 h. the leaflet moved thrice up and thrice down, and as the ascending and descending lines did not coincide, three ellipses were formed.

Fig. 148.  Desmodium gyrans:  leaf seen from above, reduced to one-half natural size.  The minute stipules unusually large.

Desmodium gyrans (Tribe 6).—­A large and full-grown leaf of this plant, so famous for the spontaneous movements of the two little lateral leaflets, is here represented (Fig. 148).  The large terminal leaflet sleeps by sinking vertically down, whilst the petiole rises up.  The cotyledons do not sleep, but the first-formed leaf sleeps equally well as the older ones.  The appearance presented by a sleeping branch and one in the day-time, copied from two photographs, are shown at A and B (Fig. 149), and we see how at