--A glass filament was fixed obliquely to the summit
of a cotyledon, rising .2 of an inch above the ground; but by the third
morning it had grown to exactly thrice this height, so that the distance of
the bead from the mark below was greatly increased, consequently the
tracing (Fig. 51) was much more magnified on the first than on the second
day. The upper part of the cotyledon changed its course by at least as much
as a rectangle six times on each of the two days. The plant was illuminated
by an obscure light from vertically above. This was a necessary precaution,
as on the previous day we had traced the movements of cotyledons placed in
a deep box, the inner side of which was feebly illuminated on one side from
a distant north-east window, and at each observation by a wax taper held
for a minute or two on the same side; and the result was that the
cotyledons travelled all day long to this side, though making in their
course some conspicuous flexures, from which fact alone we might have
[page 65]
concluded that they were circumnutating; but we thought it advisable to
make the tracing above given.
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