Thus with different species, and with
different individuals of the same species, there were many gradations from
a single diurnal movement to oscillations as complex as those of the
Ipomoea and Cassia. The opposite cotyledons on the same seedling move to a
certain extent independently of one another. This was conspicuous with
those of Oxalis sensitiva, in which one cotyledon might be seen during the
daytime rising up until it stood vertically, whilst the opposite one was
sinking down.
Although the movements of cotyledons were generally in nearly the same
vertical plane, yet their upward and downward courses never exactly coin-
[page 110]
cided; so that ellipses, more or less narrow, were described, and the
cotyledons may safely be said to have circumnutated. Nor could this fact be
accounted for by the mere increase in length of the cotyledons through
growth, for this by itself would not induce any lateral movement. That
there was lateral movement in some instances, as with the cotyledons of the
cabbage, was evident; for these, besides moving up and down, changed their
course from right to left 12 times in 14 h.
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