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Show 330 1\IODIFIED CIRCUM:NUTATION. 0HAP. VII. Averrlwa bilimbi (Oxalidro).-It has long been known,"'frrstly, that the leaflets in this genus sleep; secondly, that they move spontaneously during the day; and thirdly, that they are sensitive to a touch; but in none of these respects do they differ essentially from the species of Oxalis. They differ, however, as Mr. R. I. Lynch t has lately shown, in their spontaneous movements being strongly marked. In the case of Ll. bilimbi, it is a wonderful spectacle to behold on a warm sunny day the leafletij one after the other sinking rapidly downwards, and again ttscending slowly. Their movements rival those of Desmodium yyruns. At night the leaflets hang vertically down; and now Fig. 1:32. A1>Crrhoa bilim~i: leaf asleep; drawing r ed need. they arc motionlosR, but this may be due to the ?PPO:si~e ones beino- prossed ton-ether (Fio·. 132). 'l1ho main pebole JS m con-stanbt movement nd uring tho~-> day, but no careful obs~rvn, f wns were made on it. The following diagrams are graphiC representations of the variations in the anglo, which a given leaflet makes with the vertical. The observations were made as follows. The plant growm. o- 1. n a pot was k ep t m· •n" J11· ncr l1 teiDI)e. t'ature, the petiole of theb leaf to be observed pom· r m g sf r·,a 1o-ht at b . f the observer bcino- separated from him by a vertical pane 0 glass. The p' ctiol~ was secured so that the basal joint, or pul, v inus of one of tho lateral leaflets was at the cen t 1.o 0 f a gradut a ted a' rc placed. close bchm. d t.ho l ca.f l e t · A fi r1 8. glass. filamf ethno was fixed to tho leaf, so as to project like a contmuatwn ° • Dr. Bruce 'Philo. ophical Trans.,' 1185, P· 3jG. t 'Jouruul Linn. Sue.,' vol. xvi. Hl77, P· 2:.31. CHAP. VII. SLEEP OF LEAVES. 331 midrib. This filament acted as an index; and as the leaf rose and fell, rotating about its basal joint, its angular movement Fig. 13;J, Ave11'/ioa bitamb · • 1 • . . . I, angu a1 movements ot a leatfet dul'lng 1ts even1ng descent, when going to sleep. Temp. 78°-8t° F. could be reco d db d' . JlOS't' r e Y rea mg off at short mtervals of time tho 110 D of the glass filament on the graduated arc. In order |