14 of an inch.
Fig. 32. Helianthus annuus: circumnutation of hypocotyl, with filament
fixed across its summit, traced on a horizontal glass in darkness, from
8.45 A.M. to 10.45 P.M., and for an hour on following morning. Movement of
bead magnified 21 times, here reduced to one-half of original scale.
Helianthus annuus (Compositae).--The upper part of the hypocotyl moved
during the day-time in the course shown in the annexed figure (Fig. 32). As
the line runs in various directions, crossing itself several times, the
movement may be considered as one of circumnutation. The extreme actual
distance travelled was at least .1 of an inch. The movements of the
cotyledons of two seedlings were observed; one facing a north-east window,
and the other so feebly illuminated from above us as to be almost in
darkness. They continued to sink till about noon, when they began to rise;
but between 5 and 7 or 8 P.M. they either sank a little, or moved
laterally, and then again began to rise. At 7 A.M. on the following morning
those on the plant before the north-east window had opened so little that
they stood at an angle of 73o above the horizon, and were not observed any
longer.
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