These seedlings
had stood for two days in the same position before a north-east window. In
the morning, up to about 11 A.M., they moved in zigzag lines towards the
light; and at night they again became almost upright through apogeotropism.
After about 11 A.M. they moved a little back from the light, often crossing
and recrossing their former path in zigzag lines. the sky on this day
varied much in brightness, and these observations merely proved that the
hypocotyls were continually moving in a manner resembling circumnutation.
On a previous day which was uniformly cloudy, a hypocotyl was firmly
secured to a little stick, and a filament was fixed to the larger of the
two cotyledons, and its movement was traced on a vertical glass. It fell
greatly from 8.52 A.M., when the first dot was made, till 10.55 A.M.; it
then rose greatly until 12.17 P.M. Afterwards it fell a little and made a
loop, but by 2.22 P.M. it had risen a little and continued rising till 9.23
P.M., when it made another loop, and at 10.30 P.M. was again rising. These
observations show that the cotyledons move
[page 19]
vertically up and down all day long, and as there was some slight lateral
movement, they circumnutated.
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