[page 4]
forms of circumnutation; as again are the equally prevalent movements of
stems, etc., towards the zenith, and of roots towards the centre of the
earth. In accordance with these conclusions, a considerable difficulty in
the way of evolution is in part removed, for it might have been asked, how
did all these diversified movements for the most different purposes first
arise? As the case stands, we know that there is always movement in
progress, and its amplitude, or direction, or both, have only to be
modified for the good of the plant in relation with internal or external
stimuli.
Besides describing the several modified forms of circumnutation, some other
subjects will be discussed. The two which have interested us most are,
firstly, the fact that with some seedling plants the uppermost part alone
is sensitive to light, and transmits an influence to the lower part,
causing it to bend. If therefore the upper part be wholly protected from
light, the lower part may be exposed for hours to it, and yet does not
become in the least bent, although this would have occurred quickly if the
upper part had been excited by light.
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