At 7 A.M. on the following morning
(Sept. 26th) they occupied nearly the same level as on the previous
morning, as shown in the diagram: they then began to open or sink in the
usual manner. The diagram leads to the belief that the great periodical
daily rise and fall does not differ essentially, excepting in amplitude,
from the oscillations during the middle of the day.
Lotus Jacoboeus (Leguminosae).--The cotyledons of this plant, after the few
first days of their life, rise so as to stand almost, though rarely quite,
vertically at night. They continue to act in this manner for a long time
even after the development of some of the true leaves. With seedlings, 3
inches in height, and bearing five or six leaves, they rose at night about
45o. They continued to act thus for about an additional fortnight.
Subsequently they remained horizontal at night, though still green
[page 36]
and at last dropped off. Their rising at night so as to stand almost
vertically appears to depend largely on temperature; for when the seedlings
were kept in a cool house, though they still continued to grow, the
cotyledons did not become vertical at night.
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