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During
the whole of this time it bent outwards and downwards, so as to become more
and more nearly horizontal. The strongly marked zigzag line in the figure
on p. 248 (Fig. 111), shows that this was effected by modified
circumnutation; and during the latter part of the time there was much
ordinary circumnutation on a small scale. The movement in the diagram is
magnified between 10 and 11 times. It exhibits a clear trace of
periodicity, as the leaf rose a little each evening; but this upward
tendency appeared to be almost conquered by the leaf striving to become
more and more horizontal as it grew older. The angles which two older
leaves formed together, were measured in the evening and about noon on 3
successive days, and each night the angle decreased a little, though
irregularly.
Fig. 112. Acanthus mollis: circumnutation of young leaf, traced from 9.20
A.M. June 14th to 8.30 A.M. 16th. Apex of leaf 11 inches from the vertical
glass, so movement considerably magnified. Figure here reduced to one-half
of original scale. Temp. 15o - 16 1/2o C.
(23.


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