Two older seedlings were similarly observed,
excepting that one of them was kept in the dark; their hypocotyls also
circumnutated, but in a more simple manner. The cotyledons on a seedling
exposed to the light fell from the early morning until a little after noon,
and then continued to rise until 10.30 P.M. or later. The cotyledons of
this same seedling acted in the same general manner during the two
following days. It had previously been tried in the dark, and after being
thus kept for only 1 h. 40 m. the cotyledons began at 4.30 P.M. to sink,
instead of continuing to rise till late at night.
[page 50]
Nolana prostrata (Nolaneae).--The movements were not traced, but a pot with
seedlings, which had been kept in the dark for an hour, was placed under
the microscope, with the micrometer eye-piece so adjusted that each
division equalled 1/500th of an inch. The apex of one of the cotyledons
crossed rather obliquely four divisions in 13 minutes; it was also sinking,
as shown by getting out of focus. The seedlings were again placed in
darkness for another hour, and the apex now crossed two divisions in 6 m.
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