Consequently they both bend
upwards until the arch becomes vertical. During the whole of this process,
even before the arch has broken through the ground, it is continually
trying to circumnutate to a slight extent; as it likewise does if it
happens at first to stand vertically up,--all which cases have been
observed and described, more or less fully, in the last chapter. After the
arch has grown to some
[page 99]
height upwards the basal part ceases to circumnutate, whilst the upper part
continues to do so.
That an arched hypocotyl or epicotyl, with the two legs fixed in the
ground, should be able to circumnutate, seemed to us, until we had read
Prof. Wiesner's observations, an inexplicable fact. He has shown* in the
case of certain seedlings, whose tips are bent downwards (or which nutate),
that whilst the posterior side of the upper or dependent portion grows
quickest, the anterior and opposite side of the basal portion of the same
internode grows quickest; these two portions being separated by an
indifferent zone, where the growth is equal on all sides.
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