They are
therefore much less sensitive than those of the last species; but
they made two revolutions, following the sun, rather more rapidly,
viz., in 3 hrs. 30 m. and 4 hrs. The internodes do not revolve.
Ampelopsis hederacea (Virginian Creeper).--The internodes apparently
do not move more than can be accounted for by the varying action of
the light. The tendrils are from 4 to 5 inches in length, with the
main stem sending off several lateral branches, which have their tips
curved, as may be seen in the upper figure (fig. 11). They exhibit
no true spontaneous revolving movement, but turn, as was long ago
observed by Andrew Knight, {31} from the light to the dark. I have
seen several tendrils move in less than 24 hours, through an angle of
180 degrees to the dark side of a case in which a plant was placed,
but the movement is sometimes much slower. The several lateral
branches often move independently of one another, and sometimes
irregularly, without any apparent cause. These tendrils are less
sensitive to a touch than any others observed by me. By gentle but
repeated rubbing with a twig, the lateral branches, but not the main
stem, became in the course of three or four hours slightly curved;
but they seemed to have hardly any power of again straightening
themselves.
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