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Show 262 CIRCUl\'lNU'l'A'riON OF LEAVES. CHAP. lV. and 3 were so young that their epinastic growth, which serves to bring them down into a horizontal position, ov rpowerecl cv ry other kind of movement. In only one genus, Cannal>i , di<l the leaves sink in the evening, and Krans attributes this movement to the prepotency of their epinastic growth. rrhat the periodicity is determined by th <.htily alternations of lio·ht and darkness there can har<lly be a <1oubt, as b . will hereafter be shown. InsectiVorous plants are very little affected, as far as th ir movements arc concerned, by light; ancl h nee probably it is that their leaves, at least in the C<lses of S<:trracenia, Drosom, and Diomca, do not move periodically. rrhe upwtud move· ment in the evening is at first slow, and with cliffercnt plants begins at very difi'crcnt hours ;-with Glaucium tts early as 11 A.M., commonly between 3 and 5 P.M., but sometimes as late as 7 P.M. It should be observed that none of the leaves d scribed in this chapter (except, as we believe, those of Lrupinus speciosus). possess a pulvinus; for the pcrio<1icttl movemcnt.s of leaves thus provided have generally been amphfie<l into so-called sleep-movements, with whieh we are not here concerned. The fact of loaves ancl cotyledons fr quently, or even generally, rising a little in the evening ancl sinking in the morning, is of interest as giving the foundation from wbi ·h the speeialisod sleep· movements of many leaves and cotyledons, not Fro· vided with a pulvinus, have been developed. The above periodicity should be kept in mi1l(l, by ~~y one considering the problem of the horizontal ~os1~wn ~f leaves and cotyledons during the day, wh1lst 1llumt· natecl from above. CHAP. v. MODIFIED CIRCUl\'INU'l'A'l'ION. 2G:J CHAPTER V. MoDIFIED CmculiiNU'l'A'l'ION '• CLIMBING f> LAN'l'S ; .E~ PINASTIC AND HYPONASTIO MOVEMENTS. Oircumnutation modifiocl through innate causes or through tho a t: off elJx te• rnal condition•s -Innate oauses-01u' n bm' g P1 a nts; s1. m.1 cla nJ.Otyil o t eu mov~ments Wlfh those of ordinary plants. increased ampli-tude; occnsJOnal .points of di.fferencc-Epinnstic' growth of oun, ~~a;es-l;ryrona~tJC growth of the hypocotyls and epicotyls oi scm~ ~nos- oo ~ed hps of climbing and other plants due to modified ~Jrc~mnui~twn- Ampolopsis tricuspidata- 'mithia Pf 1'. 8trulghtenm"' of tho t' d t 1 unc u- •• .b 1p ue o 1yponasty-Epinastic growth and <'l!Cu~nnutntlon of the flower-peduncles of 'l'rifol' . l Oxuhs carnosa.. mm 1opens nn< T~E radiclos, hypocoty ls and epicoty ls of seedlin<r pfants, oven l>eforc they emerge f]:om the oTound an~ a terw. ards th e co t y 1c <.1 o ns, are all contm. uabJ ly cir'c um-nutatmg · . S o l· t l·S w·i th the stems, stolons, flower-f~ edu~c;es, a~d leaves of older plants. vV c mc.ty there-thor e ' In1e.r w1th a cons·l _u, erable degree of safety t'h at all t . h? growmg parts of all plants circumnutate. Althoug·h Is mov.e me n t ' m· 1't s or,u, ·m ary or unmodified state eaiptphe arsd . m s ome cases to be of service to plan~ ts ' nut etr' ll'ectly or indu · ·c.c t ly -lO.I! I• m• stancc, the cu• cnm-' th ta Ifonhof the radicle in penetrating the oTotmd or tha. o ·ht e arched h ypoco t Y1 and cp1· Cotyl1· nb breaki'n o-roug the surface- t · . , · · b 0 h ye cucumnutatwn 1s so o·eneral r rat er so . l b ' supp 't umversa a phenomenon, that we cannot ose l to have b . . d .I! • pose. We .ccn gmne. 101' any speCial pnr-kn must beheve that 1t follows in some nn-grooww. n way from th e manner m. wh .l Ch vegetable tissncR i-::: li';l I Jl '' I '· .::i ''"' / •''' '..'", . : :. fl |