On several occasions we were much struck with this fact, whilst
observing the circumnutation of highly sensitive seedlings, which were
unintentionally illuminated rather obliquely, or only at successive
intervals of time.
Fig. 168. Beta vulgaris: circumnutation of hypocotyl, deflected by the
light being slightly lateral, traced on a horizontal glass from 8.30 A.M.
to 5.30 P.M. Direction of the lighted taper by which it was illuminated
shown by a line joining the first and penultimate dots. Figure reduced to
one-third of the original scale.
[For instance two young seedlings of Beta vulgaris were placed in the
middle of a room with north-east windows, and were kept covered up, except
during each observation which lasted for only a minute or two; but the
result was that their hypocotyls bowed themselves to the side, whence some
light occasionally entered, in lines which were
[page 421]
only slightly zigzag. Although not a single ellipse was even approximately
formed, we inferred from the zigzag lines - and, as it proved, correctly--
that their hypocotyls were circumnutating, for on the following day these
same seedlings were placed in a completely darkened room, and were observed
each time by the aid of a small wax taper held almost directly above them,
and their movements were traced on a horizontal glass above; and now their
hypocotyls clearly circumnutated (Fig.
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