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Show 230 CITICU:MNU1'ATION OI~' LEAVES. 011AP. IV. light in which it had long remained, and a filament was fixed at the distance of ·4 of an inch from the apex of a yonng leaf nearly 4 inches in length. Its movements wore then traced during three days, but the tracing is not worth giving. The leaf fell during the whole morning, and rose in the evening and during the early part of tho night. The ascending and descending lines did not coincide, so that an inogular ellipse was formed each 24 h. The basal part of the midrib did not move, n.s was ascertained by measuring at successive periods t1to anglo which it formed with the horizon, so that the movement wn.s confined to the terminal portion of the leaf, which moved throngh an angle of 11° in the course of 24 h., and the distance travelled by the apex, up and down, was between · 8 and · 9 of an inch. In order to ascertain the effect of darkness, a filament was fixed to a leaf 5~ inches in length, borne by a plant which after forming a head had produced a stem. Tho loaf was inclined 44° above the horizon, and its movements were traced on n. vertical glass every hour by the aid of a taper. During the first day tho leaf rose from 8 A.M. to 10.40 P.M. in a slightly zigzag course, the actua.l distance travelled by the apex hcing ·67 of an inch. During the night tho loaf fell, whereas it ought to have risen; and by 7 A.M. on the following rooming it hacl fallen · 23 of an inch, and it continued falling until 9.40 A.M. It then rose until 10.50 P.M., but the rise was interrupted by one considerable oscillation, that is, by a fall and re-ascont. During the second night it again fell, but only to a very short distance, and on the following morning 1·e-ascended to a very short distance. Thus the normal course of tho leaf was greatly disturbed, or rather completely inverted, by the absence of light; and the movements were likewise greatly diminished in amplitude. We may add that, according to :Mr. A. Stephen Wilson,* the young leaves of the Swedish turnip, which is a hybrid between B. olemcea and rapa, draw together in the evening so much "that the horizontal breadth diminishes about 30 per cont. of the daylight breadth." Therefore the leaves must rise con-siderably at night. (5.) Dianthus caryophyllus (Caryophyllere, Fam. 26).- The * 'Trans. Bot. Soc. Edinburgh,' ""1. xiii. p. 32. With respect to 1 lw origiu of the Swedish turnip, see Durwin,' Animals and Plants umlcr Domcstica tiun,' 2nd t:dJt. vol. i. p. :34::1:. CHAP. IV. DICOTYLEDONS. 231 terminal shoot of a young plant, growing very vigorously, was selected for observation. The young leaves at first stand up vertically and close together, but they soon bend outwards and downwards, so as to become horizontal, and often at the same time a little to one side. A filament was fixed to tho tip of a young leaf whilst still highly inclined, and the first dot was made on the vertical glass at 8.30 A.M. Juno 13th, but it curved downwards so quickly that by 6.40 A.M. on the following morning it stood only a little above tho horizon. In Fig. 96 Fig. 96. I 0 I lh j 1 .f'O~pm13. ~~ g; ~------------~1~ } \Lo'a.m.t#h 10•as'p.m.16Jfl - -; ~ ~ 10"4s'p.m.t4t,\~ Dianthus caryophyllus: circum nutation of young leaf, traced from 10.15 P.M. June 13th to 10.35 P.M. 16th. Apex of' leaf stood at the close of our observations, Sf inches from the vertical gla s 'so tracing not greatly magnified. The leaf was 5t inches long. Tc~p. 15t0-17 ~° C. the long, slightly zigzag line representino· this rapid downward b course, which was somewhat inclined tob the left is not O'iven · ~u t the :fi ~re shows the highly tortuous and 'z igzag cbo urse,• A gether Wlth some loops, pursued during the next 21 days. ~ the leaf continued to move all the time to the left, it is evident that the Z·i gzag 1m· e represents many C·l rcumnutations. le~B.) ~amellia Japon~ca ~Came~liacere, Fam. 32).-A youngish hl WhiCh together with Its petwle was 2!! inches in length ~,tnd :~~arose !rom a side branch on a tall bush, bad a filament of 400 ~to Its apex. This loaf sloped downwards at an angle neath the horizon. As it was thick and rigid, and its |