Fig. 188. Oxalis carnosa: movements of flower-peduncle, traced on a
vertical glass: A, epinastic downward movement; B, circumnutation whilst
depending vertically; C, subsequent upward movement, due to apogeotropism
and hyponasty combined.
[page 506]
In order to trace this upward movement, a filament was fixed to a
sub-peduncle bearing a capsule nearly ripe, which was beginning to bend
upwards by the two means just described. Its course was traced (see C, Fig
188) during 53 h., by which time it had become nearly upright. The course
is seen to be strongly zigzag, together with some little loops. We may
therefore conclude that the movement consists of modified circumnutation.
The several species of Oxalis probably profit in the following manner by
their sub-peduncles first bending downwards and then upwards. They are
known to scatter their seeds by the bursting of the capsule; the walls of
which are so extremely thin, like silver paper, that they would easily be
permeated by rain. But as soon as the petals wither, the sepals rise up and
enclose the young capsule, forming a perfect roof over it as soon as the
sub-peduncle has bent itself downwards.
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