This may be the more safely inferred, as in young and unhealthy
specimens of other tendril-bearing plants similar rudiments may
occasionally be observed. In the bean these filaments are variable
in shape, as is so frequently the case with rudimentary organs; they
are either cylindrical, or foliaceous, or are deeply furrowed on the
upper surface. They have not retained any vestige of the power of
revolving. It is a curious fact, that many of these filaments, when
foliaceous, have on their lower surfaces, dark-coloured glands like
those on the stipules, which excrete a sweet fluid; so that these
rudiments have been feebly utilized.
One other analogous case, though hypothetical, is worth giving.
Nearly all the species of Lathyrus possesses tendrils; but L.
nissolia is destitute of them. This plant has leaves, which must
have struck everyone with surprise who has noticed them, for they are
quite unlike those of all common papilionaceous plants, and resemble
those of a grass. In another species, L. aphaca, the tendril, which
is not highly developed (for it is unbranched, and has no spontaneous
revolving-power), replaces the leaves, the latter being replaced in
function by large stipules.
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