The retreating movement apparently is due to the elasticity of the
resisting tissues. How far this oscillatory movement is general we do not
know, as not many circumnutating plants were observed by us under the
microscope; but no such movement could be detected in the case of Drosera
with a 2-inch object-glass which we used. The phenomenon is a remarkable
one. The whole hypocotyl of a cabbage or the whole leaf of a Dionaea could
not jerk forwards unless a very large number of cells on one side were
simultaneously affected. Are we to suppose that these cells steadily become
more and more turgescent on one side, until the part suddenly yields and
bends, inducing what may be called a microscopically minute earthquake in
the plant; or do the cells on one side suddenly become turgescent in an
intermittent manner; each forward movement thus caused being opposed by the
elasticity of the tissues?
Circumnutation is of paramount importance in the life of every plant; for
it is through its modification that many highly beneficial or necessary
movements have been acquired.
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