OCR Text |
Show 258 CIRCUl\INU'l'ATION OF CltYPTOGA~IS. CHAT'. IV. • 011 the Sleep of Plants the conRpicnons cil·~um- In the chapter . d , : r z·ata (Marsilen.cem, Fam. 4) Wlll be nutation of Ma?·sdea qua 1 tJ o t described. shown in Chap. I. that a very _young ,~ela- It has also be~n F· m 6) only ·4 inch in hmght, plamly ginclht (Lycopodmcere, 'ath~refore conclnuo that older plants, ciroumnutated; we may . · a would do the same. wh1lst growmo, . 7 , . (Hor)aticre Faro. 11, 1\iuscalcs).- (35 ) Lunulana vu ga1 ts ' . . The earth in an old flower-pot ':as l"ig. 120. coated with this plant, beanng gemmre. A highly _inclined frond, which projected ·3 mch above tho soil and was ·4 inch in breadth, was selected for observation. A ~lass hair of extreme tenuity, ·7~ mch in length, with its encl wluten~d, was cemented with shellac to w frond at right angles to its brc~dth; and a white Rtick with a mnllit~ black spot was driven into the s~Jl close behind the end of the hmr. The white oncl could be accurately brouo-ht into a line with the black t band clots could thus 1Jc sue· spo ' < 1 the vertical cessively mac o on glass-pla.te in front. Any movemont of tho frond would of course be exhibited and increased by the lono· glass hair; and the blackspo: t> nlacecl SO close behind tho C~( was 1' . l t the dJs· of the hair, relative Y o. . t ce of tho glass-plate Ill fron1, t~~t the movement of the end was maanified about 40 tl.i DO s· Never· 0 ·need that our Lttnttlanawzqans: ctrcumntta- theless, we are c~n-~ f 'thfulrc-tion of a frond, traced rom tracing gives a fau y m t f 9 AM Oct 25th to 8 A.M. 27th. t t' n of tho movemen s 0 . . preson a tO h observation, the plunl the frond. In the m· t er·v al s betweenT ehaec f rond, as alreactJY tatcd & ' Was covered by a small bell-glass. sufficient to exci.t e mo tion for a . cumnutation as it occurs only few minutes." ruh the plant is expose!l to tl~e lwig ehnt; even art1' fi . l )'crl t ''ls Cla 1o 1 CRAP. IV. OIRCUlYJ:NUTA'I'ION OF LEAVES. was highly inclined, and tho pot stood in front of a north-east window. During the five first cla.)'s tho frond moved downwards or became less inclined; and the long line which was traced was strongly zigzag, with loops occasionally formed or nearly formed; and this indicated oircumnutation. Whether tho sinking was due to epinastic growth, or apheliotropism, we do not know. As the sinking was slight on the fifth day, a new tracing was begun on the sixth day (Oct. 25th), and was continued for 47 h.; it is here given (Fig. 120). Another tracing was made on the next day (27th) and the frond was found to be still circumnutating, for during 14 h. 30 m. it changed its course completely (besides minor changes) 10 times. It was casually observed for two more days, and was seen to be continually moving. The lowest members of the vegetable series, the Thallogens, apparently circumnutate. If an Oscillaria be watched under the microscope, it may be seen to describe circles about every 40 seconds. After it has bent to one side, the tip first begins to bend back to the opposite side and then the whole filament c~m~s over in the same direction. Hofmeister* has given a mmute account of the curious, but Jess regular though constant, ~ovements of Spirogyrn: during 2.t h. the filament moved 4 times to the left and 3 times to tho right, and he refm·s to a movement at right angles to the above. The tip moved at the rate of about 0·1 mm. iu five minutes. He compares the movement with the nutation of the higher plants. t vVe shall hereafter see that heliotropic movements result from modified circum~ utation, and as unicellular Moulds bend to the light we may mfer that they also circmnnutate. CONCLUDING REMARKS ON THE 0IRCUMNUTATION OF LEAVES. The circumnutating movements of young leaves in 33 genera, belonging to 25 families, wiJely distributed F * 'Ueber die Bewegungen dcr aden der Spirogyra princeps: ~~hr~shefte des V m·eins; fii1· vater-t landlScbe Naturkunde in Wiirtembero-,' 1874, p. 211. in t, Zukalalsoremarks (as quoted Journal R. Microscop. Soc.,' 1880, vol. iii. p. 320) that the movements of Spirulina, a member of the Oscillatorie.e, are closely analogous ''to the well-known rotation of growing shoots and tendrils." s 2 |