This
treatment did not injure the leaflets, for they went to sleep in the usual
manner, and long retained their sensitiveness. the movements of one of them
were traced during 49 h., as shown in Fig. 158. On the first day the
leaflet sank down till 11.30 A.M., and then rose till late in the evening
in a zigzag line, indicating circumnutation. On the second day, when more
accustomed to its new state, it oscillated twice up and twice down during
the 24 h. This plant was subjected to a rather low temperature, viz., 62o -
64o F.; had it been kept warmer, no doubt the movements of the leaflet
would have been much more rapid and complicated. It may be seen in the
diagram that the ascending and descending lines do not coincide; but the
large amount of lateral movement in the evening is the result of the
leaflets bending towards the apex of the leaf when going to sleep. Another
leaflet was casually observed, and found to be continually circumnutating
during the same length of time.
The circumnutation of the leaves is not destroyed by their being subjected
to moderately long continued darkness; but the proper periodicity of their
movements is lost.
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