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Show 334 MODIFIED CIRCUMNU'rATION. CnAr. VII. Fig. 13.'5. CHAP. VII. SLEEP OF LEA YES. 335 32o c. 14 oscillations of a few degrees occnrrecl in 19 m. On the other hand, an oscillation may be much slower; thus a leaflet was observed (temperature 25° C.) to rise during 40 m. before it fell and completed its oscillation. Fig. 136. I I \ :: :1 l ~ f I I I I I I I : / : / / 0 I I ',' /' Porlieria hygrometril'a (Zygophyll ro ). -The leaves of this plant (ClliJi,m form) are from 1 to It inches in length, and bear as many as 16 or 17 small leaflets on each side, which do 11ot stand opposite one another. They arc articulated to tho petiole, and tho petiole to tho branch by a pulvinus. We must premise that apparently two forms are confounded under the same name: the leaves on a bush from Chi I i, which was sent to us from Kow, boro many leaflets, whilst thol'le on I)lants in the Botanic Garden at Wun:bmg bore only 8 or 9 pairs; and the whole character of tho bushes appeared somewhat different. We shall al. o see that they differ in a remarkable phyRiological peculiarity. On the Chilian plant the petioles of tho younger lea.vcs on upright branches, stood horizon tally during the day, and at night sank down vertically so as to depend pamllel and close to the branch beneath. Tho petioles of rather older 1 avos did not become at night vertically dopres. d, but only highly inclined. In ono instance we found a branch which hnd Policria !ly!)romctricc~ : C'irgrown perpendicularly downwards, cumnutation and nycti-nnd th t· 1 tropic tno1·ements of p ·- e pe 10 es on it moved in the sarue tiule of leal', traced from ,_/ ~tion relatively to the braneh as 9.35 A.lll. July 7th to JUst stated, and therefore moved up- about midnight on the Wards . 0n h · 8th. Apex of leaf 7~ Orlzontal branches the inches front the Ycrt icaJ ~oungerpetiolcs likewi o move at njght gi:lss. Tcmp.19!0-20~°C. Ill the same direction as before that is towards th ' ' ~-~ 0 branch, and arc consequently then extended hori-zonlQJJy; but it is remarkable that the older petioles on the |