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Show 308 MODIFIED 'lll 'Ul\1NU'fATION. CflAI'. VI. heen described in the first chapter. The experiment was a superfluous one, but pots with seedlingR of O.Tosea andjloribunrla were turned upside down, as FiOon aFi the cotyledons began to show any signs of sleep, and this made no difference in their movements. Leguminosre.-It may be ·eon in o:u· list ~lm~ the cotyledons of several species in nino p;cnPra., widely chHtnlmtc<l through· out the Family, sleep at night; ancl this probably .is the ca;c with many others. The cotyledons of all these F>peCJes are provided with a pulvinus; and the movement in all is continued during many days or weeks. In Ca.Rsia the co.tyleuons of tho ten species in the list ri c up vertiCal!! at mght and come into close contact with one another. \\ e obRcrvcd that those of 0. florida opened in the morning rn.ther later than those of U. glauca and pubescens. The mov.cmcnt is e~actly the same in G. mimosoides as in the oth r RpCCJeR, though Its sub .. cquently developed leaves sleep in a different manner. ~he cotyledons of an eleventh species, namely, 0. nodosa, are thwlc and fleshy, and do not rise up at night. The circumnuta~ion o: the c~ty· ledon1:1 during the day of G. tol'a ha~:; been descnbccl m the fiTs! chapter. Although the cotyl dons of 8mithict Sl'?lsitil'a ro.se from a horizontal position in the mi lcllo of the day to a vertw~l one at night, those of S. Pjundii, which are .thick and fleshy, d](l not sleep. When .llfimosa pudim and alh1d£t Jmvc been kept at a sufficiently high temperature during the day, the cotyl.edons come into clo e contact at night; otherwiRo they mc.rely nse ~Jl almost vertically. Tho circumnutation of thoHe of. M. pudtw has been described. The cotyledons of a Bauhima from Stt Catharina in .Brazil stood during tho day at an angle .or. abou 5U0 above the horizon and at night rose to 77°; but 1t 18 ?ro· bable that they would have clo ed completely, if the seedlmgs had been kept in a warmer place. b Lotus.-In three species of Lotus tho cotyledons were o s~rve\1 to sleep. Those of L. Jacobreus present tho singular ca~e 0 r-no rising at m.g ht m. any conspi· cuous. mann01 . for the first dD ort 6 days of their life, and the pulvinus is not well cl?v~~ft di~· this period. Afterwards the sleeping movement 18 t' d ,, . 1 ng con !flUe. played, though to a variable degree, anu 18 0 . with the \Ve shall hereafter meet with a nearly parallc: rs~Jebeli'i are leaves of Sida rlwmb1julia. Tho co:-yledons 0 . ·th' respect only slightly raised at night, and. d1ffcr much m 18 from the three species in our list. CriAP. VI. RLEEP OF COTYLEDONS. Trifolium.- The germination of 21 species was observed. In most of them the cotyledons rise hardly at all, or only slightly, at night; but those of T. glornemtttm, striatum and incarnatum rose from 45° to 55° above the horizon. With T. subte1·raneum, leucanthemum and strictum, they stood up vertically; and with T. strictum the rising movement is accompanied, as we shall see, by another movement, which makes us believe that the rising is truly nyctitropic. We did not carefully examine the cotyledons of all the species for a pulvinus, but this organ was distinctly present in those of T. subtermn eum and st1· iclum ; whilst there was no trace of a pulvinus in some species, for instance, in T. resupinatum, the cotyledons of which do not rise at night. Trifolium subterraneum.-The blades of the cotyledons on the first day after germination (Nov. 21st) were not fully expanded, being inclined at about 35° above the horizon; at night they rose to about 75°. Two days afterwards tho blades at noon were horizontal, with the petioles highly inclined upwards; and it is remarkable that the nocturnal movement is almost wholly confined to the blades, being effected by the pulvinus at their bases; whilst the petioles retain day and night nearly the same inclination. On this night (Nov. 23rd), and for some few succeeding nights, the blades rose from a horizontal into a vertical position, and then became bowed inwards at about an average angle of 10°; so that they had passed through an angle of 100°. Their tips now almost touched one another, their bases being slightly divergent. The two blades thus formed a highly inclined roof over the axis of the seedling. This movement is the same as that of the terminal leaflet of the tripartite leaves of many species of Trifolium. After an interval of 8 days (Nov. 29th) the blades were horizontal durino- the ~y, and vertical at night, and now they were no longer b~wed mwards. They continued to move in the same manner for the :oll~wing two months, by which time they had increased greatly In SIZe, their petioles being no less than · 8 of an inch in length, an~ t~o ~rue le~ ves bad by this time been developed. rifuhum stnctum.-On the fi1·st day after germination the ~ot~ledons, which are provided with a pulvinus stood at noon h or~zontally, and at night rose to only about 45° above the onzon. Four days afterwards the seedlings were again ob-served at n· ht d . . Jg , an now the blades stood vertiCally and were ~~~t~tact, excepting the tips, which were much deflexed, so ey faced the zenith. At this age the petioles are curved |