At 7
A.M. on the following morning they were as much expanded as at any hour on
the previous day. The cotyledons of another young seedling, exposed to the
light, were fully open for the first time on a certain day, but were found
completely closed at 7 A.M. on the following morning. They soon began to
expand again, and continued doing so till about 5 P.M.; they then began to
rise, and by 10.30 P.M. stood vertically and were almost closed. At 7 A.M.
on the third morning they were nearly vertical, and again expanded during
the day; on the fourth morning they were not closed, yet they opened a
little in the course of the day and rose a little on the following night.
By this time a minute true leaf had become developed. Another seedling,
still older, bearing a well-developed leaf, had a sharp rigid filament
affixed to one of its cotyledons (85 mm. in length), which recorded its own
movements on a revolving drum with smoked paper. The observations were made
in the hot-house, where the plant had lived, so that there was no change in
temperature or light. The record commenced at 11 A.
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