On the Motions of the Tendrils of Plants . 34 T 



substituted ; but to this substance the tendrils did not iir- 

 dicale any disposition to approach. The position of the 

 glass was then changed, and care was taken to adjust its 

 surface to the varying position of the sun, so that the light 

 reflected might continue to strike the tendrils; which then 

 receded from the glass, and appeared to be strongly repulsed 

 by it. 



The tendrils of the ampelopsis very closely resemble 

 those of the vine, in their internal orjianizalion, and in 

 originating from the alburnous substance of the plant; and 

 in being, under certain circumstances, convertible into fruit 

 stalks. The claws or claspers of the ivy, to experiments 

 upon which I shall now proceed, appear to be cortical pro- 

 trusions only; but to be capable (1 have reason to believe) 

 of becoming perfect roots, under favourable circumstances, 

 {Experiments in every respect very nearly similar to the pre- 

 ceding, were made upon this plant; but I found it neces- 

 sary to place the different substances, to which I proposed 

 that the claws should attempt to attach themselves, almost 

 in contact with the stems of the plants. I observed that 

 the claws of this plant evaded the light, just as the tendrils 

 of the ampelopsis had done; and that they sprang only 

 from such parts of the stems as were fully, or partially, 

 shaded. 



A seedling plant of the peach tree, and one of the am- 

 pelopsis and ivy, were placed nearly in the centre of the 

 house, and under similar circumstances; except that sup- 

 ports, formed of very slender bars of wood, about four 

 inches high, were applied to the ampelopsis and ivy. The 

 peach tree continued to grow nearly perpendicularly, with 

 a slight inclination towards the front and south side of the 

 house, whilst the stems of the ampelopsis and ivy, as soon 

 as they exceeded the height of their supports, inclined many 

 points from the perpendicular line, in the opposite direction. 



It appears therefore that not only the tendrils and claws 

 ■of these creeping dependent plants, but ihat their stems 

 also, are made to recede from light, and to press against the 

 opake bodies, which nature intended to support and protect 

 them. 



M. Decandole, I believe, first observed that the succulent 

 shoots of trees and herbaceous plants, which do not depend 

 upon others for support, nre bent towards the point frou! 

 which they receive light, by the contraction of the cellular 

 substance of their bark, upon that side, and I believe hi^* 

 opinion to be perfectly well founded. The operation of 

 light upon the tendrils and stems of the ampelopsis and 



ivy 



