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Show 51G MODIFIBD CIRCUMNUTATION. CHAP. X. which was already curved 36° beneath tho horir.on, was obRorverl from 11 A.l\'I. J uly 22nd to tho 27th, by which latter date it had become vertically dependent. Its course during tho first 12 ll. is shown iu Fig. 180, and its position on the three Fig. 19 1. Trifolium suiJteri'Ctnewn : circumnutating movement of peduncle, whllst the flowerhead was burying itself in s<1n<i, with the reflcxerl tip~ of the calyx gtill visible; traced 1rom 8 A.'M. July ~Gt h to 9 A.M. on 27th. Glass filament fixed transYe rse1y ncross peduncle, near flower-head. succeeding morninp:s until the 25th, when it was nearly vertical. During the first day tho peduncle cloarlj· circumnutatod, for it moved 4 timeR down and 3 times up; and on each succeeding clay, a~ it sank downwards, tho same movement continued, but was only occasionally obf;crved and was loss strongly marked. It should be stated that theRe ]Wtluncles were ohservccl under a double skylight in tho house, and that they generally moved downwal'<ls very much more slowly than those on plants growing out of doors or in the grccnlwur;c. Tho movement of au other vertically dependent peduncle with the flowerhead standing half an inch above the ground, was traced, and again when it first touched tho ground; in both cases irregular ellip~es wore described every 4 or 5 h. A peduncle on a plant wbrch had hoen brought into tho bouse, Fig. 192. moved from an u11right into a vertically dependent po~iiion in a sin glc clay ; and here the couroe during the fir~t 12 h. was nmtrly straight, but with a few well-mark_cd zigzags which betrayed the cs entral £, ·ijutium sn~terrw,ewn: moYe- IJ.,"tlll'O o•· the movement. J;astly, ment of same pcdunele, with •• l flowe r-head completely buried . tho circurnnuhttion of a peduncle beneath t he sand; traced from. was traced dnring 51 h. whilst in 8 A.l\1. to 7. 15 P.M. on July 29th._ tho act of burying itself obliquely iu a little heap of sand. After it hac.l buried_i~self to suchv~ (lopth that the tips of tho sepals. were alone vunl>lc, the abo :finTu·e (Fi()' 191) was tracou during '25 h. When the flo 1tvler-her. a d had o c· ompletely disappeared beneath t h e san d ' 'a n o 1.c r tracing was macle during 11 h. 45 m. (Fig. 102) ; and here agam we sec that the peduncle was circumnutating. CuAP. X. GEO'l'RO 'lBl\T. !)17 Anyone who will observe a flower-head burying it.·clf, wil l ht· nvinced that the rocking movcmoHt, duo to tho contimwrl c? cumnutation of 1 he peduncle, phtys an important part in 1 be :. Com:idering ihat the flowcr-~1ondr-.; arc very light, !hat. the peduncles are loug, thin, and :fl cxJblc, ancl thn.t they am;e ho111 flexible branches, it is incrGclible that a.n object as lJlunt ar-; om· of these Aowcr-heacls could penetrate tho g1·ou11d by mcnns of the growing force of tho peduncle, unless it wore aided by tho rocking movement. After a flower-head has ponetmtccl t lw ground to a small depth, another and efficient age qcy comes into play; tho central rigid aborted flowers, each terminating in 1iw long claws, curve up towards tho }led uncle; and in doing so can hardly fail to drag the head down to a greater depth, nid d as this action is by tho circumuuta.ting movernent, which confumes after the flower-head has completely buried itself. Th(· aborted flowers thns act something like tho hanr1R of tho moJo, which force the earth backwanls and tho hocly forwarclR. It is well known that the Reed-capsules of various widely distinct plants either bmy tbcmsol vcs in the ground, Ol' nro produced from imperfect flowers developed beneath tho F;urfn.co. Besides the present case, two other well-marked insta11ces will be immediately given. It is l)l'Obahlc that one chief good tlms gained is the protection of tho seeds from animals which prey on them. In the case of 1'. subtenanewn, the seeds arc not only concealed by being buried, hut arc lilwwise protected by bci11g closely surrounded by tho rigid, n.hol'tccl flowo1·s. \Y e may the more confidently infer that protection is hero aimed at, bflcau.-o the seeds of several species in this sn.mo gcnns are protected in other ways ;"' namely, by the swelling and closure of tho calyx, or hy the persistence a.ud bonding down of tho stn.nclal'Cl-pctal, &c. But the most curious instance is thn.t of '1'. ytobowm, in which the upper flowers arc sterile, as in '1'. subl(rrwwum, but arc hen· developed into large brushes of hnirs which envelop and protcet the seed-bearing flowers. Nevertheless, jn all those cas .· tlw capsules, with their seeds, may profit, a.s Mr. T. Thiselton Dyer has remarked,t by their being kept somewhat damp; and t ho advantage of such dampness perhaps throws light on the proRenee of tho absorbent hai1·s on tho buried flower-heads of '1'. slllittl'l'atteurn. According to Mr. Bentham, as quoted by Mr. Dycl', , • Vnncher, 'IIist. Phys. del-l liunt&! d'Europe,' tom. ii. p. llO. t See his inten·s tino· nrLic lo iu 'Nu.tu rc,' A pril '1t11, iS78, p . 446. |