He who has read Sachs' recent Essay
on the vertical
[page 276]
and inclined positions of the parts of plants* will see how difficult a
subject this is, and will feel no surprise at our expressing ourselves
doubtfully in this and other such cases.
A plant, 20 inches in height, was secured to a stick close beneath the
curved summit, which formed rather less than a rectangle with the stem
below. The shoot pointed away from the observer; and a glass filament
pointing towards the vertical glass on which the tracing was made, was
fixed to the convex surface of the curved portion. Therefore the descending
lines in the figure represent the straightening of the curved portion as it
grew older. The tracing (Fig. 123, p. 274) was begun at 9 A.M. on July
10th; the filament at first moved but little in a zigzag line, but at 2
P.M. it began rising and continued to do so till 9 P.M.; and this proves
that the terminal portion was being more bent downwards. After 9 P.M. on
the 10th an opposite movement commenced, and the curved portion began to
straighten itself, and this continued till 11.
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