222 CIRCUMNUTATION OF STOLONS. CHAP. IV. 



respect, was observed daring the same two days, but only two 

 inches of the terminal portion was allowed to project freely and 

 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 circumnutate when it first began 

 to bend down, as may be observed in the present diagram, and 

 as was still more evident in the last case, when a longer portion 

 of the stolon was left unsupported. On the following day 

 (26th) the stolon moved twice up and twice down, but still con- 

 tinued to fall ; in the evening and 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. The 

 lines generally extend in a vertical plane, and this 

 may probably be attributed to the effect of the weight 

 of the unsupported end of the stolon ; but there 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 and in winding between 

 the stems of the surrounding plants, the observations 

 above given render almost certain. 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. This must be a considerable advantage to the 

 plant in spreading from its parent-stock; but we are 

 far from supposing that the power has been gained 

 by the stolons for this purpose, for circumnutation 

 seems to be of universal occurrence with all growing 

 parts ; but it is not improbable that the amplitude 

 of the movement may have been specially increased 

 for this purpose. 



