. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. NYCTITBOPJG MOVEMENTS. 409. lOGo. The ample revolving inovement is not conflned to stems, iiiit is observed in some modified branches and leaves, for ex- ample in certain ten- drils, etc. A single instance will serve to show the remarkable nature of the move- ment in the case of the tendrils of Echi- nocystis lobata, as de- scribed b}' Darwin:^ '' These are usually inclined at about 46° above the horizon, but they stiffen and straighten themselves so as to stan
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. NYCTITBOPJG MOVEMENTS. 409. lOGo. The ample revolving inovement is not conflned to stems, iiiit is observed in some modified branches and leaves, for ex- ample in certain ten- drils, etc. A single instance will serve to show the remarkable nature of the move- ment in the case of the tendrils of Echi- nocystis lobata, as de- scribed b}' Darwin:^ '' These are usually inclined at about 46° above the horizon, but they stiffen and straighten themselves so as to stand upright in a part of their circular course ; namely, when the3' approach and have to pass over the summit of the shoot from which they arise. If they had not possessed and exercised this curious power, they would infallibly have struck against the summit of the shoot and been arrested in their course. As soon as one of these tendrils with its three branches be- gins to stiffen itself and rise up verticallj', the revolving motion becomes more rajjid ; and as soon as it has passed over the point of difficulty, its motion coinciding with that from its own weight causes it to fall into its previously inclined position so quickly that the apex can be seen travelling like the hand of a gigantic ; 1064. Jfyctitropic, or sleep, movements. The foliar organs of manj- plants assume at nightfall, or just before, positions unlike those which they have maintained during the day. In many cases the drooping of the leaves at night is suggestive of rest, and the name given by Linnaeus to this group of phenomena, namely, "the sleep of plants," seems appropriate. But in numer- ous cases the nocturnal position is one of obvious constraint, and considerable force has to be expended in lifting the leaf to 182 1 Power of Movement in Plants, 1880, p. 266. Ftg. 181. Leaf of Coronilla rosea at night, fDarwin.) FiQ. 182. Leaf of White Clover. ^, day position ; B, night position. (
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