OCR Text |
Show 350 MODIFIED CIR 'Ul\INUTATION. CHAP. VII. 'Vith T. Pwnnonic~tm tho first true loaf waR generally unifoliate but sometimes trifoliate, or again partially lobed and in a1~ intermediate condition. Oi1·wmnutntion.- Sachs d scrib d in 1863 * tho SJ10n tanoous up and down movement' of tho leafl et of 11 • incanwtwn, when kept in darkness. Pfeffer made many observations on the imilar movements in '1'. pralt?tse.t llo states that tho terminal leaflet of this species, ob erved at different times, passed through angles of from 30° to 120° in the comso of from l i 1o 4 h. Wo observed the movements of T. subte?Taneum, res 11pinntmn, and repens. 'l'njoli11m suut,rmnemn.-A petiole 'iras f'Ocurcd close to the base of the three leaflets, and th movement of the terminal leaflet was traced during 26} h., as shown in the figure on the next page. Between 6.45 A.M. and G P. :II. tho :tpcx moYcd 3 times up and 3 times down, completing 3 ollipseB in 11 h. 15 m. The ascending and de. cending lines , tand nearer to one another than is usual with roo 't plant s, yet thoro was some lateral motion. At 6 P.M. the gr at 110 ·tnrnal rise conunoncod, and on the next morning the sinking [ the leaflet was continued until 8.30 A.M., after which hour it circnnmutatcd in tho manner just described. In tho fi gure thu great nocturnal rise and tho morning fall arc greatly abbreviated, from the want of space, and are merely r prcsontctl by a F-hort curved line. 'l'he leaflet stood horizontally wh n at a point a little beneath the middle of tho diagram; so that during the daytime it oscillated almost equally above and beneath a horizontal position. At 8.30 A.M. it stood 48° beneath tho horizon, and by lUlO A.M. it had risen 50° above the horizon; o that it passed through 98° in 3 h. By the aid of tho tracing w u::;cortained that tho distance travelled in tho 3 h. by tho apex of this leaflet was 1 · 03 inch. If we look at the figure, and prolong upwards in our min<l's eye the short curved broken line, which repro· sents the nocturnal course we sec that tho latter movement is merely an exaggeration 01: prolongation of one of the di~·nal ellipses. The same leaflet had been observed on tho prevwus day, and the course then pursued was almost identically the same as that here described. * 'Flora,' 1So3, p. 497. 'Die Period. Bcwegungen,· 1875, pp. 35, 52. CHAP. VII. SLEEP OF LEA VBS. 351 Trifolium rest,tpinatum.-A plant loft entirely free was placed before a north-east window, in such a position that a terminal leaflet projected at right angles to the source of the light, the sky being uniformly clouded all day. The movements of this leaflet were traced during two days, and on both were closely similar. Tho (j executed on the second day are shown in Fig. 143. The obliquity of the several lines is due partly to the manner in which the leaflet was viewed, and partly to its having moved a little towards the light. From 7.50 A.M. to 8.40 A.M. the leaflet fell, that is, the awakening movement was continued. It then rose and moved a little laterally towards the light. At 12.30 it retroo-raded and at 2.30 resu~ed it~ original course, having th~s completed a small ellipse during tho middle of the day. In the evening it rose rn.piclly, and by 8 A.M. on the followin(7 morning had returned t~ exactly the same spot as on the PI'evious morning The line representing th~ nocturnal course ought ht~ be extended much Igher . up ' an d . IS here abbrevJ.ated into a short ' Fig. 142. |