I have thought it worth while to annex a tracing of
the course pursued by the upper internode (the movement of the
tendril being neglected) of a young plant from 8.40 A.M. to 9.15 P.M.
The course was traced on a hemispherical glass placed over the plant,
and the dots with figures give the hours of observation; each dot
being joined by a straight line. No doubt all the lines would have
been curvilinear if the course had been observed at much shorter
intervals. The extremity of the petiole, from which the young
tendril arose, was two inches from the glass, so that if a pencil two
inches in length could have been affixed to the petiole, it would
have traced the annexed figure on the under side of the glass; but it
must be remembered that the figure is reduced by one-half.
Neglecting the first great sweep towards the light from the figure 1
to 2, the end of the petiole swept a space 4 inches across in one
direction, and 3 inches in another. As a full-grown tendril is
considerably above two inches in length, and as the tendril itself
bends and revolves in harmony with the internode, a considerably
wider space is swept than is here represented on a reduced scale.
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