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The pinnae move forwards
and at the same time sink downwards, whilst the main petiole rises
considerably. With respect to the degree of movement: the two terminal
pinnae of one specimen formed together an angle of 100o during the day, and
at night of only 38o, so each had moved 31o forwards. The penultimate
pinnae during the day formed together an angle of 180o, that is, they stood
in a straight line opposite one another, and at night each had moved 65o
forwards. The basal pair of pinnae were directed
Fig. 160. Acacia Farnesiana: A, leaf during the day; B, the same leaf at
night.
during the day, each about 21o backwards, and at night 38o forwards, so
each had moved 59o forwards. But the pinnae at the same time sink greatly,
and sometimes hang almost perpendicularly downwards. The main petiole, on
the other hand, rises much: by 8.30 P.M. one stood 34o higher than at noon,
and by 6.40 A.M. on the following morning it was still higher by 10o;
shortly after this hour the diurnal sinking movement commenced. The course
of a nearly full-grown leaf was traced during 14 h.


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