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Show 66 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. A filament was next fixed to a cotyledon only i of an inch in h · ht hich was illuminated exclusively frpm above, and as rog ,w . 'ill . d . •t was kept in a warm greenhouse, 1t grew :ap1 Y.' an ~o" ~here could be no doubt about its cir~umn"';ltatwn, for It dcscnbed a fi Ul'e of 8 as well as two small ellipses m 5! hours. . . :e hrodium molle (Filices).-A seedling fern of ~his species p came up by chance m a flower- Fig. 53. pot near its parent. The frond, as yet only slightly lobed, was only ·16 of an inch in length and ·2 in breadth, and was supported on a rachis as fine as a hn,ir and ·23 of an inch in height. A very thin glass filament, which projected for a length of ·36 of an inch, was fixed to the end of the frond. The movement was Ncphrodiu:m molle: circumnutati~n so highly magnified that the of very young frond, traced m (F' 53) t b fully darkness on horizontal glass, figure Ig. canna e from 9 AM. to 9. P.M. Oct. 30th. trusted; but tho frond was Movement of bead magnified 48 constantly moving in a complex times. manner, and the bead greatly changed its course eighteen times in the 12 hours of observation. Within half an hour jt often returned in a line almost parallel to its former course. The greatest amount of movement occurred :Fig. 54. between 4 and 6 P.M. The circumnutation of this plant is interesting, because the species in the genus Lygodium are well known to circumnutate conspicuously and to twine round any neighbouring object. Selaginella Ilraussii (?) (Lycopodiaccro). -A very young plant, only ·4 of an inch in height, had sprung up in a pot in the not-house. An extremely fine glass filament was fixed to the end of the frond- Sclaginella Kra?tssii (?) : circumnutation of young plant, kept in darkness, tr~ced from 8.45 A.M. to 10 P.M. Oct. 31st. like stem and tho movement of the bead traced on a horizontal glass. 'It changed its course severn! times, as shown in Fig. 54, whilst observed during 13 h. 15m., and returned at night to a point not far distant from that whe:Q.ce it bad started in the morning. There can be no doubt that tills little plant circumnutated. CHAP. II. OIRCUMNU'rATION OF SEEDLINGS. 67 CHAPTER II. GENERAL CONdiDEUATIONS ON THE MOVEMEN'l'S AND GHOWTH 01!' SEEDLING PLAN'l'S. Generality of the circumuutating movement_.:_Radicles, their circumnutation of service-Manner in which they penetrate the groundManner in which hypocotyls and other organs break through t!Je ground by being arched-Singular manner of germination in Megarrhiza, &c.-Abortion of cotyledons- Circumnutation of hypocotyls and epicotyls whill:lt still buried and inched-Their power of straightening themselves-Bursting of the sced-coats-Inhel'ited etfect of the arching process in hypogean hypocotyls-Cireumnutatiou of hypocotyls and epicotyls wheu ercct-Circumnutation of cotyledons-Pulvini or joints of cotyledons, duration of their activity, rudimentary in Oxalis comiculata, their developmentSensitiveness of cutylodons to light and consequent disturbance of their periodic movements-Sensitiveness of cotyledons to contact. THE circumnutating movements of the several parts or organs of a considerable number of seedling plants have been described in the last chapter. A list is here appended of . the Families, Cohorts, Sub-classes, &e., to which they belong, arranged and numbered according to the classification adopted by Hooker.* Any one who will consider this list will see that the young plants selected for observation, fairly represent the whole vegetable series excepting the lowest cryptogams, and the movements of some of the latter when mature will hereafter be described. As· all the seedlings which were observed, including Conifers, Cycads and Ferns, which belong to the most ancient * As given in the 'General System of Bo.ta~y/ by Le M. :aout and Dccaisne, 1873. |