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Show 240 CIRCUMNU'l'A'IION OF LEAVES. CnAP. IV. t . 1 V"S only 1·2 inch in length, had a filament fixed cxter-pe 10 nally ea l'o n""g tho midrib of, the stl·l l close d lo b ~s, wthhl. ~ h · · l 1 prOfJectec at right angles to the petiole. I~ the. cvemng 1s ca com-pleted an olhpso m tho course of 2 h. On Fig. 106. the following clay (Sopt. 25th) its move\\ I ~ .>J ments wero traced during 22 h.; and we see in Fig. 106 that it moved in tho same general direction, duo to the str~ighten_ing of the leaf, but in an extremely z1gzag hne. This line represents several drawn-out or modified ellipses. There can therefore bo no doubt that this young leaf circumnutated. A rather old, horizontally extended leaf, with a filament attached along tho under sido of the midrib, was next observed during 7 h. It hardly moved, but when one of its sensitive hairs was touched, the blarl.es cloRcd, though not very quickly. A new dot was now made on the glass, but in tho course of 14 h. 20 m. there was hardly any change in the position of the filament. Wo may therefore infer that an old and only moderately sensitive leaf docs not circum· nutate plainly; but we shall soon soo Dionma muscipula: cir· that it by no moans follows that such cumnutation of a. a leaf is absolutely motionless. vVo may young and expanding 1 f m a leaf, traced on a hori- further infer that the stimu us ro zontal glass in dark- touch does not rc-excite plain circumnn· ness, from noon Sept. tation. 24th to 10 A.M. 25th. A ~other full-m·own leaf had a filament Apex of leaf 13! ..o..u. b~ ·a f the inches from the glass, attached externally along one Sl 0 0 so tracing consider- midrib and parallel to it, so that tllo fila· ably magnified. t would move if the lol>es clo. ed. ~t men h f the sens1· should be first stated that, although a touc on one~ 11 often tive hairs of a vigorous leaf causes it to close qmc: ~~Jution almost instantly, yet whon a bit of damp meat or t;OID 1 0 80 of carbonate of ammonia is placed on the lobes, the~ c osf the slowly that generally 24 h. 1. s Tequr·r ec l £0 1. the complet10n od did act. The above leaf was first observed for 2 h. 30 ~;~n for 6 not circumnutate, but it ought to have been obsei CHAP. IV. DICOTYLEDONS. 241 longer period; although, as we have seen, a young leaf completed a fairly large ellipse in 2 h. A drop of an infusion of raw meat was then placed on tho leaf, and within 2 h. the glass filament rose a little; and this implies that the lobes had begun ro close, and perhaps the petiole to rise. It continued to rise with extreme slowness for the next 8 h. 30m. The position of the po~ ~as then (7.15 P.M., Sept. 24th) slightly changed ancl an additiOnal ~rop of the infusion given, and a new tracing was begun (F1g. 107). By 10.50 P.M. the filament had risen ?nly a lit~le more, and it fell during the night. On the follow~ ng morn~ng the lobes were closing more quickly, and by 5 P.JII. It was eVIdent to the eye that they had closed considerably· by 8,~ P.M. thi~ was still plainer, and by 10.45 P.M. the mar~inal spikes were mterlocked. The leaf fell a little during the ni()'ht and next morning (25th) at 7 A.M. the lobes were complete!; shut. The course pursued, as may be seen in the figure, was Fig. 107. s·48'p.m. 10•4:1p:m.a:;~h vro·a.m.2(J~.4 J D7~ mus?ipula: cl~sure of the lobes and circumnutation of a full-grown .qe~' Whilst absorbmg an infusion of raw meat, traced in darkness from · s. P.M. Sept. 24_th to 9 A.M. 26th. Apex of leaf St inches fro:U the vertical glass. Figure here reduced to two-thirds of original scale. strongly zigzag, and this indicates that the closino- of the lobes was combined with the circum nutation of the b whole leaf· ~:d there cannot be much doubt, considering how motionles~ theleafwas during 2 h. 30m. before it received the infusion . at the absorption of the animal matter had excited it t~ ~Ircumnutate. The leaf was occasionally observed for the next .tour days, but was kept in rather too cool a place· nevertheless I co.n. tm' ue d t o m· rcumnutate to a small extent, 'a nd the lobes' remamed closed. 1i is some~imes stated in botanical works that the lobes close ~r s ~pat mght; but this is an error. To test the statement itn~ry: ong glass filaments were fixed inside the two Jobes of lea~e~, and the distances between their tips were measured be de~:d.le of the day and at night; but no difference could The previous b t' wh 1 1 0 ° serva IOns 1·elate to the movements of the e eafJ but the lobes move independently of the petioleJ and R |