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Show 214 CIROUMNU'fA'fiON OF STOLONS. OnAP. IV. fore, sooner or later, bend to all sides ; but after a stem has bent in any one direction, it commonly bends back at :first in nearly, though not quite, the opposite direction; and this gives the tendency to the formation of ellipses, which arc generally nanmr, but not so narrow as those described by stolons and leaves. On the other hand, the figures sometimes approach in shape to circles. Whatever the figure may be, the course pursued is often interrupted by zigzags, small triangles, loops, or ellipses. A stem may describe a single large ellipse one day, and two on the next. With different 1lants the complexity, rate, and amount of movement differs much. The stems, for instance, of Ibcris and Azalea described only a single large ellipse in 24 h.; whereas those of the Deutzia made four or :five deep zigzags or narrow ellipses in 11~ h., and those of the Trifolium three triangular or quadrilateral figures in 7 h. CrRCUMNUTA.TION oF STOLONS oR RuNNERS. Stolons consist of much elongated, flexible l.mmches, which run along the surface of the ground anu form roots at a distance from the parent-plant. rrhey are therefore of the same homological nature as stems; and the three following cases may be added to the twenty previously given cases. Fragaria (cultivated garden var.): Rosacere.-A plant growing in a pot had emitted a long stolon; this was supported by a stick, so that it projected for the length of several inches bori· zontally. A glass :filament bearing two minute triangles of paper was affixed to the terminal bud, which was a little np· turned; and its movements were traced during 21 h., as shown in Fig. 85. In tho course of the first 12 h. it moved twice up and twice down in somewhat zigzag lines, and no doubt t_ra· veiled in tho same manner during the night. On tho followJllg CHAP. IV. CIROUMNUTATION OF STOLONS. 215 morning after an intervnl of 20 h. the apex stood a little higher than it did at first, and this shows that the stolon had not been Fig. 85. ./ JO"p.m. / J0.451a.'m 18~"' ( / Fragaria: circumnutation of stolon, kept in darkness, traced on verti cal glass, from 10.45 A.l\1. May 18th to 7.45 A.M. on 19th. ac~d on within this time by geotropism;* nor had its own weight caused it to bend downwnrds. dOn the following morning (19th) the glass filament waR .etached and refixed close behind the bud, as it appeared pos- 8~'.1~ t?at the circumnutation of the terminal bud and of the a JOmmg part of the stolon might be different. The movement ;~snow traced during two consecutive days (Fig. 86). Dming five ~st day the filament travelled in the course of 14h. 30m. unes up and four times down, besides some lateral movemenht. On the 20th the course was even more complicated nnd cISanh ardly be foll o~c d m. thc fi gurc; but tho filament move' d in ·at least five t1mcs up and five times down, with very little N * Dr: A. B. Frank states (' Die v:turhche wagerechte Richtung th~ pttanzentheilen,' 1870, p. 20) e stolons of this plant are acted on by geotropism, but only after a considerable interval of time. |