Thus, the
great sweeps made by the stems of twining plants, and by the tendrils of
other climbers, result from a mere increase in the amplitude of the
ordinary movement of circumnutation. The position which young leaves and
other organs ultimately assume is acquired by the circumnutating movement
being increased in some one direction. the leaves of various plants are
said to sleep at night, and it will be seen that their blades then assume a
vertical position through modified circumnutation, in order to protect
their upper surfaces from being chilled through radiation. The movements
of various organs to the light, which are so general throughout the
vegetable kingdom, and occasionally from the light, or transversely with
respect to it, are all modified
* See Mr. Vines' excellent discussion ('Arbeiten des Bot. Instituts in
W?rzburg,' B. II. pp. 142, 143, 1878) on this intricate subject.
Hofmeister's observations ('Jahreschrifte des Vereins f?r Vaterl.
Naturkunde in W?rtemberg,' 1874, p. 211) on the curious movements of
Spirogyra, a plant consisting of a single row of cells, are valuable in
relation to this subject.
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