As in this position they are crowded together, and as they do
not become folded like those in the genus Oxalis, they cannot occupy a
vertically dependent position; but they are often inclined at an angle of
50o beneath the horizon. In this species, whilst the leaflets are sinking,
the petioles rise up, in two instances when the angles were measured to the
extent of 23o. The leaflets of L. sub-carnosus and arboreus, which were
horizontal during the day, sank down at night in nearly the same manner;
the former to an angle of 38o and the latter of 36o, beneath the horizon;
but their petioles
[page 341]
did not move in any plainly perceptible degree. It is, however, quite
possible, as we shall presently see, that if a large number of plants of
the three foregoing and of the following species
Fig. 137. Lupinus pilosus: A, leaf seen from vertically above in daytime;
B, leaf asleep, seen laterally at night.
were to be observed at all seasons, some of the leaves would be found to
sleep in a different manner.
In the two following species the leaflets, instead of moving downwards,
rise at night.
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