We now come to a remarkable position of the leaves when asleep, which is common to several species of Lupines.  On the same leaf the shorter leaflets, which generally face the centre of the plant, sink at night, whilst the longer ones on the opposite side rise; the intermediate and lateral ones merely twisting on their own axes.  But there is some variability with respect to which leaflets rise or fall.  As might have been expected from such diverse and complicated movements, the [page 342] base of each leaflet is developed (at least in the case of L. luteus) into a pulvinus.  The result is that all the leaflets on the same leaf stand at night more or less highly inclined, or even quite vertically, forming in this latter case a vertical star.  This occurs with the leaves of a species purchased under the name of

Fig. 138.  Lupinus pubescens:  A, leaf viewed laterally during the day; B, same leaf at night; C, another leaf with the leaflet forming a vertical star at night.  Figures reduced.

L. pubescens; and in the accompanying figures we see at A (Fig. 138) the leaves in their diurnal position; and at B the same plant at night with the two upper leaves having their leaflets almost vertical.  At C another leaf, viewed laterally, is shown with the leaflets quite vertical.  It is chiefly or exclusively the youngest leaves which form at night vertical stars.  But there [page 343] is much variability in the position of the leaves at night on the same plant; some remaining with their leaflets almost horizontal, others forming more or less highly inclined or vertical stars, and some with all their leaflets sloping downwards, as in our first class of cases.  It is also a remarkable fact, that although all the plants produced from the same lot of seeds were identical in appearance, yet some individuals at night had the leaflets of all their leaves arranged so as to form more or less highly inclined stars; others had them all sloping downwards and never forming a star; and others, again, retained them either in a horizontal position or raised them a little.

We have as yet referred only to the different positions of the leaflets of L. pubescens at night; but the petioles likewise differ in their movements.  That of a young leaf which formed a highly inclined star at night, stood at noon at 42o above the horizon, and during the night at 72o, so had risen 30o.  The petiole of another leaf, the leaflets of which occupied a similar position at night, rose only 6o.  On the other hand, the petiole of a leaf with all its leaflets sloping down at night, fell at this time 4o.  The petioles of two rather older leaves were subsequently observed; both of which stood during the day at exactly the same angle, viz., 50o above the horizon, and one of these rose 7o — 8o, and the other fell 3o — 4o at night.  We meet with cases like that of L. pubescens with some other species.  On a single plant of L. mutabilis some leaves, which stood horizontally during the day,