Dutrochet observed the completion of an ellipse in 1 hr. 20 m.; and I
saw one completed in 1 hr. 30 m. The direction followed is variable,
either with or against the sun.
Dutrochet asserts that the petioles of the leaves spontaneously
revolve, as well as the young internodes and tendrils; but he does
not say that he secured the internodes; when this was done, I could
never detect any movement in the petiole, except to and from the
light.
The tendrils, on the other hand, when the internodes and petioles are
secured, describe irregular spires or regular ellipses, exactly like
those made by the internodes. A young tendril, only 1.125 of an inch
in length, revolved. Dutrochet has shown that when a plant is placed
in a room, so that the light enters laterally, the internodes travel
much quicker to the light than from it: on the other hand, he
asserts that the tendril itself moves from the light towards the dark
side of the room. With due deference to this great observer, I think
he was mistaken, owing to his not having secured the internodes. I
took a young plant with highly sensitive tendrils, and tied the
petiole so that the tendril alone could move; it completed a perfect
ellipse in 1 hr.
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