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Ipomoea bona-nox.--The cotyledons after a few days grow to an enormous
size, those on a young seedling being 3 1/4 inches in breadth. They were
extended horizontally at noon, and at 10 P.M. stood at 63o beneath the
horizon. five days afterwards they were 4 ? inches in breadth, and at night
one stood at 64o and the other 48o beneath the horizon. Though the blades
are thin, yet from their great size and from the petioles being long, we
imagined that their depression at night might be determined by their
weight; but when the pot was laid horizontally, they became curved towards
the hypocotyl, which movement could not have been in the least aided by
their weight, at the same time they were somewhat twisted upwards through
apogeotropism. Nevertheless, the weight of the cotyledons is so far
influential, that when on another night the pot was turned upside down,
they were unable to rise and thus to assume their proper nocturnal
position.
Ipomoea coccinea.--The cotyledons whilst young do not sink at night, but
when grown a little older, but still only .


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