30 A.M. In the present instance, however, the great nocturnal
rise did not commence till 7 P.M.; but this was due to the hypocotyl having
from some unknown cause temporarily bent to the left side, as is shown in
the tracing. To ascertain positively that the hypocotyl circumnutated, a
mark was placed at 8.15 P.M. behind the two now closed and vertical
cotyledons; and the movement of a glass filament fixed upright to the top
of the hypocotyl was traced until 10.40 P.M. During this time it moved from
side to side, as well as backwards and forwards, plainly showing
circumnutation; but the movement was small in extent. Therefore Fig. 15
represents fairly well the movements of the cotyledons alone, with the
exception of the one great afternoon curvature to the left.
Oxalis corniculata (var. cuprea).--The cotyledons rise at night to a
variable degree above the horizon, generally about 45o: those on some
seedlings between 2 and 5 days old were found to be in continued movement
all day long; but the movements were more simple than in the last two
species. This may have partly resulted from their not being sufficiently
illuminated whilst being observed, as was shown by their not beginning to
rise until very late in the evening.
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