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Show 202 CIRCU:M:NUTATION OF STEl\18. CnAP. IV. ·e selected which, from being woody, or for other wer . . rrh reasons, seemed the least hkcly to cucumnutate: e observations and the diagrams were mad.c m tho manner described in the Introduction. Plants in p.ots were subjected to a proper. tcmp.eraturc, and wh1lst being observed, were kept mther m darkness or were feebly illuminated. from above. ~hey are arranged in the ord.er adopted by Hooker 1n Le Maout and Decaisne's ' System of Botany.' The. number of the family to which each genus belongs_ 1s appe~clod, as this serves to show the place of each 111 the senes. (1.) Jberis nmbellata (Cruciferro, Fam.l4).-Tho mov?~ent of tho stem of a young plant, 4 inches in hoi~ht, cons1stmg of four internodes (the hypocotyl included) bosHles a large bud Fig. 70. Jberis umbeltata: c.t rcumnutatl.o n o f s t em o f ~oun g ph·. n t ' trac.e d fcreo mof 8.30 A.M. Sept. loth to same hour on followwg morn.mg. Dtstan ram summit of stem beneath the horizontal glass 7·6 mches. Dwg·fi d reduced to half of original size. Movement as here shown ma.gm c between 4 and 5 times. on the summit, was traced, as hero shown, duri.ng 24 :~ (Fig. 70). As far as we could judge tho uppermost mch alo ~f the stem circumnutated, and this in a simple manner: Th~ movement was slow and the rate very unequal at dlffert·hen times. In part of i' ts course an u· rogu1 a r e1 11· p se ' or ra cr triangle, was completed in 6 h. 30 m. t b ·ng (2.) Brassica oleracea ( Crucifcrre ).-A very young plan ' oafrl three leaves, of which the longest was on1 Y thr ee -quar.t ersd o w iathn inch in length, was placed under a microscope, furmshe f an eye-piece micrometer, and the tip of the largest lea was CHAP. IV. CIRCUMNUTATION OF S~rEMB. 203 found to be in constant movement. It crossed five divisions of the micrometer, that is, Ji0th of an inch, in 6 m. 20 s. Thoro could hardly be a doubt that it was tho stem which chiefly moved, for the tip did not get quickly out of focus; and this would have occurred had tho movement boon confined to tho leaf which moves up or down in nearly the same vertical plane. (3.) Linum usitatissimum (Lincro, Fa.m. 39).-Tho stems of this plant, shortly before tho flowering period, arc stated by Fritz Miiller (' Jenaische Zoitschrift,' B. v. p. 137) to revolve, or circumnutate. (4.) Pelar,qonium zonale (Gcraniacoro, Fam. 4.7).-A young plant, 7! inches in height, was ob ·orvod in tho usual manner; but, in order to see tho bead at tho end of tho glass filament :Fig. 71. ,.~:::rl .--A/\s'cl;n.ll'!· ~ 12~9f!~ / ·~,i~:!Jo'p.m.tot1~ Pclar,qonium zonale: circum nutation of stem of yonng plant, feeuly illuminated from above. Movement of bead magnified about 11 times ; traced on a horizontal glass from noon on 11larch 9th to 8 A.l\1. on the 11th. and at the same time the mark beneath, it was necessary to cut off three leaves on one side. We do not know whothor it was owing to this cause, or to tho plant having previously become bent to one side through heliotropism, but from tho morning of the 7th of March to 10.30 P.M. on tho 8th, tho stem moved a.con~iderable distance in a zigzag line in tho same general ~rect10n. During tho night of the 8th it moved to some distance at right angles to its former course, and next morning (9th) stood for a time almost still. At noon on tho 9th a now tracing was begun (sco Fig. 71), which was continued till 8 A.M. on the 11th. Between noon on tho 9th and 5 P.M. on tho lOth (i.e. in the course of 29 h.), the stem described a circle. This plant therefore circumnutatcs but at a very slow rate and to a smn.U extent. ' ' C5.) !ropreolum mafus (?) (dwarfed var. called Tom Thumb); (Geramacem, Fam. 47).-Tho species of this genus climb by tho |