Power of Movement in Plants

Page 118

216 OIROU:MNU'rA'riON OF S'rOLONS. 0IIAP. IV. lateral deflection. The first and last dots mado on this second clay, viz., at 7 A.M. and 11 P.M., wore close together, showing that the stolon had not fallen or rison. Nevertheless, by com-paring its position on Fig. 86. tho morning of tho 19th and 21st, it is obvious that the stolon hacl sunk; and this may bo attri­buted to slow bending clown either from its own weight or from geotro­pism. Dming a part of tho 20th an orthogonal tracing was made by applying a cube of wood to tho vortic.'ll glass and bringing the apex of tho stolon at snc­cossivo periods into a line with ono eclgo; a dot being made each time on the glass. This tracing therefore represented very nearly tho actual amount of movement of the apex; and in tho course of ~ 11. the distance of the ex­treme dots from one an- ( other was ·45 inch. By tho same method it waR I ascertained that tho apex moved. between 7 ur. on 8oa.m.21.!' the 20th and 8 A.M. on the Fmgaria : circumnutatiou of the same stolon 21st a distance of ·82 inch. as in the last figure, observed in the same A younger ancl shorter manner, and traced from 8 A.llf. May 19th t 1 supported so to 8 A.M. 21st. s o on was. that it proJected at about 45° above the horizon and its movement was traced by tho same orthogonal method. On tho first day tho .apex. 800~ rose above the field of visjon. By tho next mormng 1t hac sunk, and the course pursuocl was now traced. during 14 h. 30 m. (Fig. 87). The amount of movement was almost tho same, CHAP. IV. OIROUUNUTATION OF S'l'OLON . 217 from side to side as up and down; and differed in this respect remarkably from the movement in tho previous cases. During the latter part of the day, viz., between 0 and 10.30 P.M., the Fig. 87. ,tr JO' a.m~oif" s•u.m D"a.m .. Fragaria: circumnutation of another and younger stolon, traced from 8 A.M. to 10.30 P.:r.r. Figure r educed to one-half of original scale. actu~l distance travelled by the apex amounterl to 1·15 inch; ~nd m the course of the whole day to at least 2·67 inch. This IS an amotmt of movement almost comparable with that of some climbing plants. 'l'hc same stolon was ob erved on tho following. day, and now it moved in a somewhat loss complex manner, m a plano not far from vertical. Tho extreme amount ~factual movement was 1·55 inch in one direction, and ·6 inch ~n ano~her direction at right angles. Dming neither of these ays di~ the stolon bond downwards through geotropism or its own wmght. Fo~r stolons stm attached to tho plant wore laid on damp sa~d m the back of a room, with thcil· tips facing tho north-enst ;~dows. Th~y wo~e thus placed because Do Vries says* that Yare apheliotropiC when exposed to tho Iio·ht of tho sun· but w. e could t · b ' 1 no pcrcmve any effect from tho above feeble degree of llumin at I' on. Wo may add that on another occnsion late in the summ er, some stolons, placed upright before a south-w' est window * 'Arbeiten Bot. lost., Wiirzburg,' 1872, p. 43-1.