On the other hand, the
cotyledons of Cucurbita ovifera moved in the normal manner during a whole
day in darkness.
Seedlings of Githago segetum were feebly illuminated from above in the
morning before their cotyledons had expanded, and they remained closed for
the next 40 h. Other seedlings were placed in the dark after their
cotyledons had opened in the morning and these did not begin to close until
about 4 h. had elapsed. The cotyledons of Oxalis rosea sank vertically
downwards after being left for 1 h. 20 m. in darkness; but those of some
other species of Oxalis were not affected by several hours of darkness. The
cotyledons of several species of Cassia are eminently susceptible to
changes in the degree of light to which they are exposed: thus seedlings of
an unnamed S. Brazilian species (a large and beautiful tree) were brought
out of the hot-house and placed on a table in the middle of a room with two
north-east and one north-west window, so that they were fairly well
illuminated, though of course less so than in the hot-house, the day being
moderately bright; and after 36 m.
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