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Show 244 CIRCUl\1NU'fATION OF LEAVES. CHAP. IV. of raw meat was placed on the leaf, which caused tho lobes to close together very slowly in the course of two clays; and the oscillations continued during this whole time and for the next two days. After nino additional days the leaf began to open nnd the margins were a little everted, and now the apex of the glass filament remained for long periods motionle s, and then moved backwards and forwards for a distance of about -duo of an inch slowly, without any jerks. N evertholess, after warming the leaf with a taper held close to it, the jerking movement recommenced. This same leaf had been observed 2~ months previously, and was then found to be oscillating or jerking. We may therefore infer that this kind of movement goes on night and day for a very long period; and it is common to young unexpamled leaves and to leaves so old as to have lost their sensitiveness to a touch, but which were still capable of absorbing nitrogenous matter. The phenomenon when well displayed, as in the young loaf just described, is a very interesting one. It often brought before our minds the idea of effort, or of a small animal struggling to escape from some constmint. (16.) Eucalyptus resinifera (Myrtacero, Fam. 94).-A young leaf, two inches in length together with tho petiole, produced by a lateral shoot from a cut-down tree, was observed in the usual manner. The blade had not as yet as· sumed its vertical position. On June 7th only a few ob. ervations wore made, and tho trn,cing merely showed that tho loaf h<ld moved three times upwards uncl three downwards. On tho following day it was observed more frc· quently; and t11o tmcings were made ( seo A and B, Fig. 108), ns a single one would have been too complicated. Tho apex: changed its course 13 times in the course of 16 h., chiefly up anrl clown, but Fig. 108. A Eucalyptus resinffera: circumnutation of a leaf, traced, A, from 6.40 A.M. to 1 P.M. June 8th ; 13, from 1 P.:M. 8th to 8.30 A.M. 9th. Apex of leaf 14~ inches from the horizontal glass, so figures considerably magnified. with some lateral movement. The actual amount of movement in any one direction was small. (17.) Dahlia (garden var.) (Compositre, Fam.122).-A fine young CHAP. IV. DICOTYLEDONS. 245 leaf~~ inc?es in 1 Ien_gth, produced by a young plant 2 foot high, growmg :1gorous y m a large pot, was directed at an angle of about 45 bene~th the horizon. On June 18th tho leaf descended from 1 1ot.A.M 6 . t1ll 11._35 A.l\1. (seo Fig. 109); it then ascended great Y 11l P.M., this ascent being probably due to the light Fig. 109. ... .'fl' 40' u.?nJDtl• 'Uf 3.l' pm.18~ ~ 20'a.ma f'"B'IO'a.m, l 20~"- ~ j Dahli!l: circum nut t' f I 20th, but with~ ~~~e~k e;f, traced from 10 .A. .llf. June 18th to 8.10 A.M. owing to the lass fil~ o 1 h .. 4~ m. on the morning of the 19th, as, to be slightl ~ d. ment pomtmg t oo. much to one side the pot had is somewha/arb~:~~ary th~f~fofle th.e relatlv~ pos~tion of the 'two tra cings the original scale A e f fuie h~re giVen JS reduced to one-fifth of of its inclinatio~ ~nd 4~e~ o h ea:f 9 lnch~s from the glass in the line • 'I m a onzontal hne. COming only f b 10.35 P.M. and rom a ove .. It zig~agged between 6 P.M. and remarked, that a:ended. a htt!e durmg. the night. It should be diagram e vertiCal distances m the lower part of the are much exa t d . < beneath th h . ggora e , as the leaf was at first deflected filament p e· t odn .z on' and a ft er. 1· t h a d sunk down wards the om e m a very oblique line towards the glass. Next |
