To what species these three latter forms
belong we do not know. We could not make out in the case of the Naples
cotton, that the position of the cotyledons at night was influenced by the
soil being more or less dry; care being taken that they were not rendered
flaccid by being too dry. The weight of the large cotyledons of the Alabama
and Sea-island kinds caused them to hang somewhat downwards, when the pots
in which they grew were left for a time upside down. It should, however, be
observed that these three kinds were raised in the middle of the winter,
which sometimes greatly interferes with the proper nyctitropic movements of
leaves and cotyledons.
[page 304]
Cucurbitaceae.--The cotyledons of Cucurbita aurantia and ovifera, and of
Lagenaria vulgaris, stand from the 1st to the 3rd day of their life at
about 60o above the horizon, and at night rise up so as to become vertical
and in close contact with one another. With Cucumis dudaim they stood at
noon at 45o above the horizon, and closed at night. The tips of the
cotyledons of all these species are, however, reflexed, so that this part
is fully exposed to the zenith at night; and this fact is opposed to the
belief that the movement is of the same nature as that of sleeping plants.
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