OCR Text |
Show 256 CIRCUMNUT A TION OF LEAVES. CUAP. IV. 5 and 6 P.M. On the next day tho loaf stood at only 0 10° abovo the horizon at 8.25 A.M., and it remained at about 15 till past 3 P.M.; at 5.40 P.M. it was 23~, and ~t 9.30 P.M. 58°; so ~hat the rise was more sudden this cvemng than on tho ])l'OVJOus e and the difference in tho angle amounted to 48°. The on, . . f d movement is obviously penodiCal, and as tho lea stoo on the first night at 55°, and on tho see~nd .night at .58° above tho horizon, it appeared very steeply mclmed. Thts case, as wo shall see in a future chapter, ought perhaps to have been included under tho head of sleeping plants. (33.) Pontederia (sp. ?) (from the highlands of St. Catharina1 Fig. 118. \-~-- /~ / Pontederia (sp. ?) : circumnutation of leaf, traced from 4.50 P:M. July _2nd to 10.15 A.M. 4th. Apex of leaf 16t inches from the I'CJ'llC~1l glass, 50 tracing greatly magm· fi e d . 'I' emp. a"u ou t 17o C. , and therefore mthcr too low. Brazil) (Pontederiacero Faro. 46).-A filament was fixed acro~d the apex of a moderat'e ly young leaf, 7 ~ inches m· b m·g h t an 1 its movements were traced during 42~ h. (see Fig. 11~). On the first evening, when the tracing was begun, and dunng !he night the leaf descended considerably. On the next mor~~ it asdended in a strongly marked zigzag line, and descen t agam. m. the evenm. g and d urm. g tho m.g ht. The movemen' therefore seems to be periodic, but some doubt is throw~ hotn ' · h ·n hma 1 this conclusion because another leaf, 8 me os 1 t:> ed appcarinO' olde; and standing more highly inclined, hohav different!;. During the first 12 h. it circumnutatcd over a CHAP. IV. CIRCUMNUTATION OF CRYPTOGAMS. 257 small space, but during the night and tho whole following day it ascended in the same general direction; the ascent being effected by repeated up and down well-pronounced oscillations. CRYPTOGAMS. (34.) Nephrodium molle (Filices, Fam. 1).-A filament was fixed near the apex of a young frond of this Fern, 17 inches in height, which was not as yet fully uncurled; and its movements were traced during 24 h. We see in Fig. 119 that it Fig. 119. Ne~hrodium molle: circum~utation of rachi , traced from 9.1.'5 A.M. l\1ay 8th to 9 A.M. 29th. F1gure here given two-thirds of original scale. plainly circumnutated. The movement was not greatly magnified !l.'l the frond was placed near to tho vertical glass, and would probably have been greater and more rapid had the day been warmer. For the plant was brought out of a warm greenhouse and observed under a skylight, where the temperature was ~ween 15oand 16° C. yve have seen in Chap. I. that a frond of . 8 ~ern,.as yet only slightly lobed and with a rachis onJy ·23 mch Ill height, plainly circumnutated.* Gr: Mr. Loomis. and Prof. Asa G Y have descnbcd (' Botanical azette,• 1880, pp. 27, 43) an extre~ely curious case of rdove~: n: 1~ .the fronds, but only in t • ~hng froncls, of Asplenium n"c .anes. They move almost 8 rapidly as the little leaflets of Desmndium (J?J1'ans, alternately b1lckwards and forwards through fi·om 20 1o 40 degrees, in a plane at right angles to that of the frunrl. The apex of the frond describes "a long and very narrow ellipse,'' sq thftt it circumnutates. But the movement differR from ordinary s |