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Show 226 CIRCUMNUTATION OF LEAVES. CHAP. IV. of many plants, for instance, those of JJrassica napits~ revolve. or ~ircumnutate · those of Allium po1-rum bend from s1de to side, ~nd if this ~ovement had been traced on a horizontal gla. s, no doubt ellipses would have been formed. Fritz Muller has describe 1 * the spontaneous revolving movements of the flowerstems of an Alisma, which he compares with those of a climbing plant. . '\Ve made no observations on the movements of the different parts of flowers. 1\~on·en, however~, has . observed t in t~~~ stamens of Sparmanma and Cereus a frem1ssement spontane, which it may be suspected, is a circumnutating movement. The circumnut.ation of the gynostcmium of Stylidium, as described by Gacl,t is highly remarkable, and a~parentl~ aids in the fertilisation of the flowers. The gynostemmm, wh1lst spontaneously moving, comes into contact with the viscid labcllum, to which it adheres, until freed by the increasing tension of the parts or by being touched. \¥ e have now seen that the flower-stems of pl:mts belonging to such widely different families as the Cruciferre, Oxalidre, Leguminosre, Primulacem, Scro· phularinere, Alismacere, and Liliacem, circumnutat~; and that there are indications of this movement m many other fctmilies. '\Vith these ~acts before ~s, bearino- also in mind that the tendnls of not a few plants b consist of modified peduncles~ we may admit without much doubt that all growmg flower-stems circumnutate. 0IRCUMNUTA'IION OF LEAVES : DICOTYLEDONR. Several distinguished botanists, Hofmeister, Sachs, Pfeffer, De Vries, Batalin, l\1illardet, &c., have ob· p. 766. Lmnrnus and 'l'reviranus (arcording to Pfefl'er, 'Die Periodischen Bcwegungen,' &c., P· 162) state that the flower-stnlks of many plu.nts occupy different positions by night and day, and we shall 81 e in the chapter on tlw 'le..-p of l'la11t~ that this im-plies circumnutation. * • Jcnnische Zeit ·ch.,' B. v. p. t1 3•3 . d R de N. Mem. de l'Ara · : Bruxellcs' tom. xiv. 1841. P· •\ t ·, Sitz~nO'bericht de~ bnt. \ ~· reins der P. Brandenburg,' xxL p. 8-:1:. CnAr. IV. DICOTYLEDONS. 227 served, and some of them with the greatest care, the periodical movements of leaves ; but their attention has been chiefly, though not exclu ·ively, directed to those which move larg ly and are commonly said to sleep at night. From considerations hereafter to b • given, plants of this nature are here exeluded, anrl will be treated of separately. As we wished to ascertain whether all young and growing leaves circumnutated, we thought that it would be sufficient if we observed between 30 and 40 genera, widely distributed throughout the vegetable series, sel cting some unusual forms and others on woody plants. All tlw plants were healthy and grew in pots. They wen· illuminated from above, but the light p rhaps was not always sufficiently bright, as many of them were observed under a skylight of grouncl-o-lass. Except in a few specified cases, a fine glass filam nt with two minute triangles of paper was fixed to the leaves, and their movements were traced on a vertical glass (when not stated to the contrary) in the manner already described. I may r peat that the broken lines represent the Ilocturnal course. ~rhe stem was always secured to a stick, close to the base of the le<Lf under observation. rrhe arrangement of the species, with the number of the Family appended, is the same as iu the case of stems. Sarrrrccnia ptwpw·ea: circumnutation of young pitcher, traced from!:! A.M. July :3nl to 10.15 A.M. 4th. Tern p. 17°- 18° C. Apex of pitcher 20 inches from glas~, so movement greatly mag( 1.) Snrracenia purpurea (Sarranified. c~nem, Fam. 11).-A young leaf, or Pitcher, 8! inches in height, with the lJln.dder swollen, but with the hood not as yet open, had a filament fixed transversely Q 2 |
