Here then we have a good opportunity for observing how
apogeotropism acts when very nearly balanced by an opposing force. For
instance, the plumule of Tropaeolum majus (see former Fig. 175) moved
towards the dim evening light in a slightly zigzag line until 6.45 P.M., it
then returned on its course until
[page 502]
10.40 P.M., during which time it zigzagged and described an ellipse of
considerable size. The hypocotyl of Brassica oleracea (see former Fig. 173)
moved in a straight line to the light until 5.15 P.M., and then from the
light, making in its backward course a great rectangular bend, and then
returned for a short distance towards the former source of the light; no
observations were made after 7.10 P.M., but during the night it recovered
its vertical position. A hypocotyl of Cassia tora moved in the evening in a
somewhat zigzag line towards the failing light until 6 P.M., and was now
bowed 20o from the perpendicular; it then returned on its course, making
before 10.30 P.M. four great, nearly rectangular bends and almost
completing an ellipse.
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