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Show 2~2 CIRCUMNUTA.TION OF STOLON,. CHAP. IV. respect, was observed during the same two days, but only two inches of the terminal portion was allowed to project freely !tncl horizontally. On the 25th it continued from 9.10 A.M. to 1.30 P.M. to bend straight downwards, apparently owing to its weight (Fig. 90); but after this hour until 10.35 P.M. it zigzagged. This fact deserves notice, for we here probably see the combined effects of the bending down from weight and of circumnutation. The stolon, however, did not circumnutn.to when it first began to bend down, as may be observed in tho pre ·ent dia gram, and u.s was still more evident in tho last cn.so, when a longer portion of the stolon was left unsupported. On tho following day (26th) the stolon moved twice up and twice down, but ,otill continued to fall; in the evening n.nd during the night it travelled from some unknown cause in an oblique direction. We see from these three cases that stolons or runners circumnutate in a very complex manner. rl,he lines generally extend in a vertical plane, aml this may probably be attributed to the effect of the weight of the unsupported end of the stolon; but thoro is always some, and occasionally a considerable, amount of lateral movement. The circumnutation is so great in amplitude that it may almost be compared with that of climbing plants. That the stolons are thus aided in passing over obstacles all(l in winclin cr between the stems of the surrounding plants, the observations above given render almost certttin. If they had. not circumnutated, their tips would have been liable to have been doubled up, as often as they met with obstacles in their path; but as it is, they easily avoid them. rrhis must be a considerable advantage to the plant in spreading from its par nt-stock; but we arc far from supposing that the power bas been gai1~ed by the stolons for this purpose, for circnmnutat~on seems to be of universal occurrence with all growmg parts; but it is not improbable that the amplitude of the movement may have been specially increased for this purpose. CnAP. IV. CIR0Ul\1NUTA.TION OF FLOWER- 'TEMS. 223 0IRCUMNUTATION OF FLOWER- TEMS. We did not think it necessary to m<tke any special observations on tho circumnutation of ilower-stems, these being axial in their nature, like stem or stolons ; but some were incidentally mauo whilst attending to other subjects, and theso we will h r briefly give. A few observations have also been mu.<le by other botanists. These taken together s uffi ·o to render it probable that all peduncles and sub-peduncles circumnutate whilst growing. Oxalis carnosa.-The peduncle which springs from tho thick and woody stem of this plant bears three or four sub-peduncles. Fig. 91. ..........___ 0x atI'~ carnosa: flower-stem, feebly illuminated from :dJove, its ci rcumnuta- 81~n traced from 9 A.M. April 13th to 9 A.llf. 15th. , ummit of flower bo mches ~eneath the horizontal glass. Movement prol>ably magnified a ut 6 t1mes. \filament with Uttle triangles of pn.per was fixed within tho c~ Yl of a flower which stood uprjght. Its movements were 0 served for 48 h.; during tho first half of thjs time the flower wfiaa fully expanded, and during the second half withered. The thgeu rme ahie re gi·v en (F I· ~. 91) represents 8 or 9 ellipses. Although n peduncle mrcumnutated, and described one large and |
