S48 On the Motions of the Tendrils of Plants. 



ivy appears to produce diametrically opposite effects, and 

 to occasion an extension o'i the cellular baik, wherever that 

 is exposed to its influence ; and this circumstance aff'ords, 

 I think, a satisfactory explanation why these plants appear 

 to seek and approach contiiiuous opake objects, just as they 

 wovild do, iF they were conscious of their own feebleness, 

 and of power in the objects, to which ihey approach, to 

 aflTord them support and protection. 



The tendril of the vine, as I have already slated, is inter- 

 nally similar to that of the ampelopsis, though its external 

 form, and mode of attaching itself, by twining round atiy 

 slender body, are very different. Some young plants of 

 this species, which had been raised in pots in the preceding 

 year, and had been headed down to a single bud, were 

 placed in a forcing-house, with the plants 1 have already 

 mentioned ; and the shoots from these were bound to slen- 

 der bars of wood, and trained perpendicularly upwards. 

 Their tendrils, like those of the ampelopsis, when first 

 emitted, pointed upwards ; but they gradually formed an 

 increasing angle with the stems, and ultimately pomted 

 perpendicularly downwards ; no object having presented 

 itself to which they could attach themselves. 



Other plants of the vine, under similar circumstances, 

 •were trained horizontally; when their tendrils gradually 

 descended beneath their stems, with which they ultimately 

 stood very nearly at right angles. 



A third set of plants were trained almost perpendicularly 

 downwards, but with an inclination of a few degrees to- 

 wards the north ; and the tendrils of these permanently re- 

 tained very nearly their first position, relatively to their 

 stems ; whence it appears that these organs, like the ten- 

 drils of the aiTipelopsis, and the claws of the ivy, are to a 

 great extent under the control of light. 



A few other plants of the same species were trained in 

 each of the preceding methods; but proper objects were 

 placed, in diflerent situations near them, with which their 

 tendrils might come into contact ; and I was by these 

 means afforded an opportunity of observing with accuracy 

 the difference between the motions of these and those of 

 the ampelopsis, under similar circumstances. The latter 

 almost immediately receded from light, by whatever means 

 that was inadc to operate upon them ; and they did not 

 subsequently show any disposition to approach the points 

 from which they once receded. The tendrils of the vine, 

 on the contrary, varied their positions in every period of 

 the day, and after, returned again during the night to the 



situations 



