During the first 1 h. 15 m. the plumule moved to the right, and during the
next two hours it returned in a roughly parallel but strongly zigzag
course. From some unknown cause it had grown up through the soil in an
inclined direction, and now through apogeotropism it moved during nearly 24
h. in
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the same general direction, but in a slightly zigzag manner, until it
became upright. On the following morning it changed its course completely.
There can therefore hardly be a doubt that the plumule circumnutates,
whilst buried beneath the ground, as much as the pressure of the
surrounding earth will permit. The surface of the soil in the pot was now
covered with a thin layer of very fine argillaceous sand, which was kept
damp; and after the tapering seedlings had grown a few tenths of an inch in
height, each was found surrounded by a little open space or circular crack;
and this could be accounted for only by their having circumnutated and thus
pushed away the sand on all sides; for there was no vestige of a crack in
any other part.
In order to prove that there was circumnutation, the move-
Fig.
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