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Show 52± SBXSI'riVENERS TO GRAVI'l'A'l'ION. CiL\P. XL vegetative point) of the tips of tile .r;t<liclcs of tho bean ( V1'oia faba), and placed them horizontnlly or vertically in chtmp ttir, em'th, and water, with the result that thc~y L 'C<Une Lowml in <tll 8orts of (Erections.* He therefore disbelieved in Ciesielski's r~ondusions. But as \\"e h.-we sccu with scvoml plant. that the tip of tho radicle is sensjtiYe to conta<"t an!] to other irritant.s, nn<l that it, tmnsmits some influence to the npp r growing part cam;ing it to lmwl, there seemed to us to l)c no a yn·im·i improl.mbility in Ciesielski's statements. 'Vo therefore determined to repeat his experiments, and to try others on several species Ly different mctho<1s. l'iciafabn.-Racliclos of this plant wore cxiondocl llori7.ontally either over water or with their lower umfacos jnst touching it. Their tips had previously boon cut o:fJ, in a direction as accurately transverse aR conlcl be dono, to different lengths, mcasmed from tho apex of tl 1e root-cap, all(t which will be specified in each case. Light was always excluded. We had previously tried 1nmdrods of nnmutilate<l m<liclcR nnclor simibr circumstances, and found that every OilO that waf.l healthy became plainly' geotropic in under 12 h. In tho ca~c of four radiclcs which had their tips cut off for a length of Hi nnn., now rootcaps and now vegetative points wore re-formed after an interval or 3 lays 20 h. ; an<.l theRe when placo<1 horizonially wore acted on by geotropism. On some other occasions thiR regeneration of the tips and reacquired R011SitivonosR occmrecl wiihin a .·omcwhat shorter time. 'rhcrcfol'OJ ra<liclus having their tips amputated should be observed in from J 2 to 48 h. after the opera.tion. Four radicles wore oxtendorl Jwrizontally with their lolrcr Rurfacos touching tho water, and with their tips cut off for.a length of only 0·5 mm. : after 23 h. throe of them were st:Ill horizontal; after 47 h. one of tlJO three became fairly geotropw; ~md after 70 h. the other two showed a trace of this action. 'fhc fourth radicle was vertically geotropic after 23lt.; but by an * 'Arbeiten des But. I11stiluts in Wiirzburg,' Heft. iii. 1873, P· 432. CHAP. :XI. TRANS:M:I'l"rED E:Fl!'EC'l,S: VIOlA. 525 accident the root-cap alone and not tho _vegetative point waf'i found to have been amputated; so tbat this case fonnud no real ception and might have been excluded. ex Five radicles wore extended horizontally like tho last, aml hatl their tips cut off for a length of lrnm.; after 22-23 h.J four of them were still horiz,mtal, and. one W<ts slightly geotropic; after 48 h. the latter had boco11lo vertical; a Slcond was alRo somell'hat geotropic; two remained approximately horizontal ; antl the last or fifth had grown in a disordered manner, for jt was inclined upwards at an angle of 63° above the hori7.on. Fourteen radicles wore extended horizontally at a little height over the water with their tips ent off for tt length of 1·5 nnn.; after 12h. all were horizontal, whilst fho control or standard specimens in the same jar were all bcHt f!Tcatly downwardH. After 24 h. several of the amputated radiclos remained horizontal, but some showed a tmco of geotropism, and ouc was plainly geotropic, for it was inclined <tt 4.0° beneath tho ltorjzon. Seven horizontally extended radides from which tho tips had been cut off for the nnusual length of 2 mm. unfortunately wcr8 not looked at until 35 h. httd elapr-;ecl; three were still horizontal, but, to our surprise, four were more OI' less plainly o-cotropic. The radicles in the foregoing cases wero measured Loforo their tips were amputatocl, and in tho course of 24 h. they had all incr~ascd greatly in longth; but the moa::mroments arc not worth giving. It is of more importance that Sachs fonnd that thij r1tte of growth of the different parts of racliclos witlt amputated tips was the same as with unruutilated 011oR. Alto· gether twenty-nine radicles wore operated ou in tho manner above described, and of these ouly a few showed any geotropic curvature within 24 h.; whereas mcliclos with umuut.ilc1ted tipH always became, as alrcc.tdy statucl, much bent down in less than half of this time. The part of the m ticle which bonus most lie~ at the diRtancc of from 3 to G mm. from the tip, n.ncl as th ' bending part continues to grow aftor the operation, thoro doe~ not seem any reason why it should not lutve been acted on by geotropism, nnloss its cmvatnro depended on some infl.ucnco transmitted from the tip. Autl we havo clear eviJ.encc of snell tran8mission in CiesielskiJs experiments, which wo repo~tted. ancl extended in the following maunor. Bea.ns wore embedcled in frittl>le peat with tho hilum down~ ards, and after their radiclcs hacl grown perpcndicubtrly dowH lor a. length of from 1 to l inch, sixteen were sclecte<l which |