In the course of the present volume it will be shown that apparently every
growing part of every plant is continually circumnutating, though often on
a small scale. Even the stems of seedlings before they have broken through
the ground, as well as their buried radicles, circumnutate, as far as the
pressure of the surrounding earth permits. In this universally present
movement we have the basis or groundwork for the acquirement, according to
the requirements of the plant, of the most diversified movements. 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
Würzburg,' B. II. pp. 142, 143, 1878) on this intricate subject.
Hofmeister's observations ('Jahreschrifte des Vereins für Vaterl.
Naturkunde in Würtemberg,' 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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forms of circumnutation; as again are the equally prevalent movements of
stems, etc., towards the zenith, and of roots towards the centre of the