The
movements of the cotyledons were also traced both on vertical and
horizontal glasses; their angles with the horizon were likewise measured at
various hours. They fell from 8.30 A.M. (October 17th) to about noon; then
moved laterally in a zigzag line, and at about 4 P.M. began to rise; they
continued to do so until 10.30 P.M., by which hour they stood vertically
and were asleep. At what hour of the night or early morning they began to
fall was not ascertained. Owing to the lateral movement shortly after
mid-day, the descending and ascending lines did not coincide, and irregular
ellipses were described during each 24 h. The regular periodicity of these
movements is destroyed, as we shall hereafter see, if the seedlings are
kept in the dark.
[page 51]
Solanum palinacanthum.--Several arched hypocotyls rising nearly .2 of an
inch above the ground, but with the cotyledons still buried beneath the
surface, were observed, and the tracings showed that they circumnutated.
Moreover, in several cases little open circular spaces or cracks in the
argillaceous sand which surrounded the arched hypocotyls were visible, and
these appeared to have been made by the hypocotyls having bent first to one
and then to another side whilst growing upwards.
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