Tendrils of another kind consist of modified flower-peduncles. In
this case we likewise have many interesting transitional states. The
common Vine (not to mention the Cardiospermum) gives us every
possible gradation between a perfectly developed tendril and a
flower-peduncle covered with flowers, yet furnished with a branch,
forming the flower-tendril. When the latter itself bears a few
flowers, as we know sometimes is the case, and still retains the
power of clasping a support, we see an early condition of all those
tendrils which have been formed by the modification of flower-
peduncles.
According to Mohl and others, some tendrils consist of modified
branches: I have not observed any such cases, and know nothing of
their transitional states, but these have been fully described by
Fritz Muller. The genus Lophospermum also shows us how such a
transition is possible; for its branches spontaneously revolve and
are sensitive to contact. Hence, if the leaves on some of the
branches of the Lophospermum were to abort, these branches would be
converted into true tendrils. Nor is there anything improbable in
certain branches alone being thus modified, whilst others remained
unaltered; for we have seen with certain varieties of Phaseolus, that
some of the branches are thin, flexible, and twine, whilst other
branches on the same plant are stiff and have no such power.
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