Even whilst the arched or doubled hypocotyl is still beneath the ground, it
circumnutates as much as the pressure of the surrounding soil will permit;
but this was difficult to observe, because as soon as the arch is freed
from lateral pressure the two legs begin to separate, even at a very early
age, before the arch would naturally have reached the surface. Seeds were
allowed to germinate on the surface of damp earth, and after they had fixed
themselves by their radicles, and after the, as yet, only
[page 13]
slightly arched hypocotyl had become nearly vertical, a glass filament was
affixed on two occasions near to the base of the basal leg (i.e. the one in
connection with the radicle), and its movements were traced in darkness on
a horizontal glass. The result was that long lines were formed running in
nearly the plane of the vertical arch, due to the early separation of the
two legs now freed from pressure; but as the lines were zigzag, showing
lateral movement, the arch must have been circumnutating, whilst it was
straightening itself by growth along its inner or concave surface.
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