. The power of movement in plants. Plants; Botany. Chap. Vil. SLEEP OF LEAVES. 335 Fig. 136. 32° C., 14 oscillations of a few degrees occurred m 19 m. On the other hand, an oscillation may be much slower; thus a leafloJ was observed (temperature 25° 0.) to rise during 40 m. before it fell and completed its oscillation. Poiiieria hygrometrica (Zygophyllese) —The leaves of this plant (Chi!i,in form) are from 1 to IJ inches in length, and bear as many as 16 or 17 small leaflets on each side, which do not stand opposite one another. They are articulated to the petiole, and the petiole to the branc
. The power of movement in plants. Plants; Botany. Chap. Vil. SLEEP OF LEAVES. 335 Fig. 136. 32° C., 14 oscillations of a few degrees occurred m 19 m. On the other hand, an oscillation may be much slower; thus a leafloJ was observed (temperature 25° 0.) to rise during 40 m. before it fell and completed its oscillation. Poiiieria hygrometrica (Zygophyllese) —The leaves of this plant (Chi!i,in form) are from 1 to IJ inches in length, and bear as many as 16 or 17 small leaflets on each side, which do not stand opposite one another. They are articulated to the petiole, and the petiole to the branch by a pulvinus. We must premise that apparently two forms are confounded under the same name : the leaves on a bush from Chili, which was sent to us from Kew, bore many leaflets, whilst those on plants in the Botanic Garden at Wdrzbnrg bore only 8 or 9 pairs; and the whole character of the bushes appeared some- what different. We shall also see that they differ in a remarkable physio- logical peculiarity. On the Chilian plant the petioles of the younger leaves on upright branches, stood horizontally during the day, and at night sank down vertically so as to depend parallel and close to the branch beneath. The petioles of rather older leaves did not become at night vertically depressed, but only highly inclined. In one instance we found a branch which had Polkria grown perpendicularly downwards, and the petioles on it moved in the same direction relatively to the branch as just stated, and therefore moved up- wavds. On horizontal branches the younger petioles likewise move at night in the same direction as before, that is, towards the branch, and are consequently then extended hori- zontally; but it is remarkable that the older petioles on tho. hygrometrioa: rir- cumnutation and nycti- tropic movements of pe- tiole of leaf, traced from July 7th to about midnight on the 8th. Apex of leaf 7J inches from tho vertical glass. Temp. 19J°-20i° Please note that these
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