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Show 366 MODIFIED CIRCUMNU'fATION. CnaP. VII. petiole), and the movement of the whole leaf was traceu vertical glass. This was a bad plan iu some respects L on a th t . f . , uecausc e ro · d atwn o the leaflet, mdepcndontly· of its ri ·inrr 0 . f' lli b 1 a ng ra1se a~d depressed the filament; but it was the best plan fo~ our s~ecml purpose of observing whether the leaf moved much after. It h~d gone to sleep .. The plant had twined closely round a thm stick, so that the cucumnutation of tho stem was provented. Tho movement of the leaf was traced during 48 h., fr~m 9 A.M. July lOth to 9 A.M. July 12th. In the figure given (F1~. 151) we see how complicated its cour c was on both chys: durmg the second day it changed its comse greatly 13 times. The leaflets began t? go to sleep a little after 6 P.M., and by 7.15 P.M. hung vertically down and were comvletely asleep· but on both nights they continued to move from 7.15 u: to .10.40 and 10.50 P.M., quite as much as during the day; and tlns was the point which we wished to ascertain. We see in the figure t~at the grea~ sinking movement late in the evening docs not d1ffer essentially from the circumnutation durin11 the day. 0 Glycine hispida (Tribe 8).-The three leaflets sink vertically down at night. Erythrina (Tribe 8).-Five species were observed, and the le~flets of all sank vertically down at night; with 8. caffra and With a second unnamed species, the petioles at the same time rose slightly. The movements of the tcrminallcaOet of 1!:. cristagalU (with the main petiole secured to a stick) were traced from 6.40 A.M., June Bth, to 8 A.M. on the lOth. In order to observe the ny~titropic movements of this plant, it is necessary that it should have grown in a warm greenhouse, for out of doors in our climate it docs not sleep. We sec in the tracing (Fig. 152) that the leaflet oscillated twice up and down between early morning and noon; it then fell greatly, afterwards rising till 3 P.M. At this latter hour the great noctumal fall commenced. On the second day (of which the tracing is not given) there was exactly the same double o cillation before noon, but only a very small one in the afternoon. On the third morning the leaflet moved laterally, which was due to its begiuniug to assume an ol>lique position, as seems invm·iably to occur with the leaflets of this species as they grow old. On both nights after the leaflets were asleep and hung vertically down, they coutinucd to move a little both up and down, and from side to side. Erythri?ta caffra.-A filament was fixed transversely across CnAr. vn. SLEEP OF LEA YES. a terminal leaflet, as we wished to observe its movements when asleep. The plant was placed in the morning of June lOth under a skylight, where the light was not bright; and we do not know whether it was owing to this cause or to the plant having been disturbed, but the leaflet hung vertically down all day; nevertheless it circumnutated in this position, describing a figure which represented two irregular ellipses. On the next day it circumnutated in a greater degree, describing four irregular ellipses, and by 3 P.M. ~~risen into a horizontal poSitiOn. By 7.15 P.M. it was asleep and vertically dependent, but continued to circumnutate as long as observed untilll P.M. ' 6 "!10'u.7J6 .8~ Z"p.11t. 367 Fig. 152. J J J I I J I I J I I I I I ~ G~Gam.otf. I a·1 J t I I I Erythrina corallodendron. _ The movements of a terminal leaflet were traced. During the second day it oscillated four times up and four times down between 8 A.M. and 4 P.M., after which hour the great nocturnal fall commenced. On the third day the movement was equally great in amplit~ de, but was remarkably sunple, for the leaflet rose in : almost perfectly stmight e from 6.50 A.M. to 3 P M and th · ., en sank down in an ;u~lly straight line until elrtwally dependent and as eep. Er·yt.hr·ina cTistu-galt£: circumnutatJon and nyctitropic movement of terminal leaflet, 3! inch es in le.ngth, traced during 25 h.; apex of leaf 3t inches from the vertical glass .. ~' igure reduced to one-half of ongmal scale. Plant illuminated from above. temp 17.1.0_ 18!0 c. ' . 2 |
