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Those on the seedling which had been kept in almost complete
darkness, sank during the whole day, without rising about mid-day, but rose
during the night. On the third and fourth days they continued sinking
without any alternate ascending movement; and this, no doubt, was due to
the absence of light.
Primula Sinensis (Primulaceae).--A seedling was placed with the two
cotyledons parallel to a north-east window on a day when the light was
nearly uniform, and a filament was affixed to one of them. From
observations subsequently made on another seedling with the stem secured to
a stick, the greater part of the movement shown in the annexed figure (Fig.
33), must have been that of the hypocotyl, though the cotyledons certainly
move up and down to a certain extent both during the day and night. The
movements of the same seedling were traced
[page 46]
on the following day with nearly the same result; and there can be no doubt
about the circumnutation of the hypocotyl.
Fig. 33. Primula Sinensis: conjoint circumnutation of hypocotyl and
cotyledon, traced on vertical glass, from 8.


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