If their
blades or laminae were to abort, they would form true tendrils. And
of this process of abortion we can follow every step, until no trace
of the original nature of the tendril is left. In Mutisia clematis,
the tendril, in shape and colour, closely resembles the petiole of
one of the ordinary leaves, together with the midribs of the
leaflets, but vestiges of the laminae are still occasionally
retained. In four genera of the Fumariaceae we can follow the whole
process of transformation. The terminal leaflets of the leaf-
climbing Fumaria officinalis are not smaller than the other leaflets;
those of the leaf-climbing Adlumia cirrhosa are greatly reduced;
those of Corydalis claviculata (a plant which may indifferently be
called a leaf-climber or a tendril-bearer) are either reduced to
microscopical dimensions or have their blades wholly aborted, so that
this plant is actually in a state of transition; and, finally, in the
Dicentra the tendrils are perfectly characterized. If, therefore, we
could behold at the same time all the progenitors of Dicentra, we
should almost certainly see a series like that now exhibited by the
above-named three genera.
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