346 On the Motions of the Tendrils of Plants. 



have rejected this hypothesis, few or no experiments have 

 been made hy them to ascertain with what propriety the 

 various motions of tendrils, of different kinds, can be at- 

 tributed to peculiarity of organization, and the operation of 

 external causes. I was consequently induced, during the 

 last summer, to employ a considerable portion of time to 

 watch the motions of the tendrils of different species of 

 plants; and I have now the pleasure to address to you an 

 account of the observations I was enabled to make. 



The plants selected were the Virginia creeper (the am- 

 pelopsis quinquefolia of Michaux), the ivy, and the com- 

 mon vine and pea. 



A plant of the ampelopsis, which grew in a garden pot, 

 was removed to a forcing-house in the end of May, and a 

 sitiffle shoot from it was made to grow perpendicularly up- 

 wards, bv being supported in that position by a very slen- 

 der bar of wood, to which it was bound. The plant wa? 

 placed in the middle of the house, and was fully exposed to 

 the sun ; and every object around it was removed far be- 

 yond the reacii of its tendrils. Thus circumstanced, its 

 tendrils, as soon as they were nearly full grown, all pointed 

 towards the north, or back wall, which was distant about 

 eight feet: but not meeting with any thing in that direc- 

 tion, to which they could attach themselves, they declined 

 gradually towards the ground, and ultimately attached 

 themselves to the stem beneath, and the slender bar of 

 wood. 



A plant of the same species was placed at the east end 

 of the house, near the glass, and was in some measure 

 skreened from the perpendicular light; when its tendrils 

 pointed towards the west, or centre of the house, as those 

 under the preceding circumstances had pointed towards the 

 north and back wall. This plant was removed to the 

 west end of the house, and exposed to the evening sun, 

 beng skreened, as in the preceding case, from the perpen- 

 dicular light; and its tendrils, within a few hours, changed 

 their direction, and again pointeil to the centre of ihe 

 house, which was partially covered with vines. This plant 

 was then removed to ihe centre of the house, and fully ex- 

 posed to the perpendicular light, and to the sun ; and a 

 piece of dark-coloured paper was placed upon one side of 

 it, just within the reach of its tendrils; and to this sub- 

 stance they soon api)carcd to be strongly attracted. The 

 paper was then placed upon the opposite side, under similar 

 circumnances, and there it was soon followed by the ten- 

 drils, it was then reuioved, and a piece of plate glass was 



substituted j 



