OCR Text |
Show 228 CIRCUMNUTATION OF LEA VF.S. CHAP. IV. across its apex; it was observed for 48 h., and during tho whole of this time it circumnutated in a nearly similar manner, but to a very small extent. The tracing given (Fig. 03) relates only to the movements during the first 26 h. (2.) (Jluucinm l11tettm (Papaveracero, Fam. 12).-A young plant, bearing only 8 leaves, had a filament attached to the youngest leaf but one, which "~a.· 3 inches in Fig. 94-. I i t I I i I I J ! I ! I 1 I Glaucium luteum: circumnutation of young leaf, traced from 9.30 A.M. June 14th to 8.30 A.M. 16th. Tracing not much magnified, as apex of leaf stood only 5~ inuhcs from the glass. length, including the petiole. The circumnutating movement was traced during 47 h. On both days the leaf descended from before 7 A.l\1. until about 11 A.M., and then ascended slightly during the rest of the day and the early part of the night. During tho latter part of tho night it fell greatly. It did not ascend so much dming the second as during tho ftrst day, and it descended considerably lower on the second night than on the first. This difference was prollably clno to the illumination from above having been insufficient during the two days of observation. Its course during the two days is shown in Fig. 94. (3.) Grambe mar·itima (Cruciferro, F am.l4).-A leaf 0~ inches in length on a plant not growing vigorously was first observed. Its apex was in constant movement, but this could hardly be traced, from being so small in extent. The apex, however, certainly changed. its course at least 6 times in the course of 14: h. A more vigorous young plant, boar· ing only 4leaves, was then selected, and a filament was affixed to tho midrib of the third leaffrom the base, which, with the petiole, was 5 inches in length. The leaf stood up almost vertically, but the tip C'nAP. IV. DICOTYLEDONS. 229 was ~efl.ected, so that the filament p:ojected almost horizontally, and 1ts movements were traced durmg 48 h. on a vertical glass as shown in the accompanying figure (Fig. 95). We here plainl; see that the leaf was con-tinually circumnutating ; Fig. 95. but the proper periodicity lf...4o'a.m.eat?l ...... of its movements was dis- .\ turbed by its being only 8~ a •. n~. '~<;-\ dimly illuminated from J. 9..~!Mn.e3"'!1 above through a double \:\,\':i 11 • .. Jo~eo'p.1n.f!4.·!p, skylight. We infer that this was the case, because two leaves on plants grow-ing out of doors, bad their angles above the horizon ~~. measured in the middle of the day and at 9 to \ about 10 P.M. on succes- \ sive nights, and they were found at this latter ~:.:.:. h t V~50'a;m.B3 1il our o have risen by an average angle of go above their mid-day position: on the following mornine: they fell to their forme~ -{t position. Now it may be 6~50'a.m.24oq.,\~ observed in the diagram that the leaf roso during ~he second night, so that ltstoodat 6.40 A.M. higher 3':p.m.Ul~ than at 10.20 P.M. on the 0 ra~ be mm·itima: circumnutation of leaf, preceding night; and this disturbed by being insufficiently illumi-may be attributed to the nated from nbove, traced from 7.50 A.M. le~f adjusting itself to tho June 23rd to 8 A.M. 25th. Apex of leaf dim li h 15! in ch~s from the vertical glass, so that . g t, coming exclu- the tracmg was much maO'nified but is Slvely from above. here reduced to one-fourth ~f~rigin~l scale. sta(t4e. ) thBarta stshic a oler (C · 1 acea rumferre).-Hofmoister and Batalin * day W e eaves of the cabbage rise 11t night and fall hy . e covered a young 1 t b . 8 ' ' . bell-glass placin . . P an ' earmg leaves, under a large ' g It m the same position with respect to the "' 'Flora.,' 1873, p. 437. |