We believe that the leaflets, especially the two lateral ones, in performing the above described complicated movements generally bend a little downwards; but we are not sure of this, for, as far as the main petiole is concerned, its nocturnal movement is largely determined by the position which the leaf happens to occupy during the day.  Thus one main petiole was observed to rise at night 59o, whilst three others rose only 7o and 9o.  The petioles and sub-petioles are continually circumnutating during the whole 24 h., as we shall presently see.

The leaves of the following 15 species, M. officinalis, suaveolens, parviflora, alba, infesta, dentata, gracilis, sulcata, elegans, coerulea, petitpierreana, macrorrhiza, Italica, secundiflora, and Taurica, sleep in nearly the same manner as just described; but the bending to one side of the terminal leaflet is apt to fail unless the plants are growing vigorously.  With M. petitpierreana and secundiflora the terminal leaflet was rarely seen to bend to one side.  In young plants of M. Italica it bent in the usual manner, but with old plants in full flower, growing in the same pot and observed at the same hour, viz., 8.30 P.M., none of the terminal leaflets on several scores of leaves had bent to one side, though they stood vertically; nor had the two lateral leaflets, though standing vertically, moved towards the terminal one.  At 10.30 P.M., and again one hour after midnight, the terminal leaflets had become very slightly bent to one side, and the lateral leaflets had moved a very little towards the terminal one, so that the position of the leaflets even at this late hour was far from the ordinary one.  Again, with M. Taurica the terminal leaflets were never seen to bend towards either of the two lateral leaflets, though these, whilst becoming vertical, had bent towards the terminal one.  The sub-petiole of the terminal leaflet in this species is of unusual length, and if the leaflet had bent to one side, its upper surface could have come into contact only with the apex of either lateral leaflet; and this, perhaps, is the meaning of the loss of the lateral movement.

The cotyledons do not sleep at night. the first leaf consists of a single orbicular leaflet, which twists at night so that the blade stands vertically.  It is a remarkable fact that with M. Taurica, and in a somewhat less degree with M. macrorrhiza and petitpierreana, all the many small and young leaves produced during [page 348] the early spring from shoots on some cut-down plants in the greenhouse, slept in a totally different manner from the normal one; for the three leaflets, instead of twisting on their own axes so as to present their lateral edges to the zenith, turned upwards and stood vertically with their apices pointing to the zenith.  They thus assumed nearly the same position as in the allied genus Trifolium; and on the same principle that embryological characters reveal the lines of descent in the animal kingdom, so the