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, 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 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 39°. 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 17°–17½° 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. 147. Arachis hypogoea: A, leaf during the day, seen from vertically above; B, leaf asleep, seen laterally, copied from a photograph. Figures much reduced. Fig. 148. Desmodium gyrans: leaf seen from above, reduced to one-half natural size. The minute stipules unusually large.