condition; and yet they have retained during this whole period the
innate power of spontaneously revolving and twining, whenever their
shoots become elongated under proper conditions of life. Most of the
species of Phaseolus are twiners; but certain varieties of the P.
multiflorus produce (Leon, p. 681) two kinds of shoots, some upright
and thick, and others thin and twining. I have seen striking
instances of this curious case of variability in "Fulmer's dwarf
forcing-bean," which occasionally produced a single long twining
shoot.

Solanum dulcamara is one of the feeblest and poorest of twiners: it
may often be seen growing as an upright bush, and when growing in the
midst of a thicket merely scrambles up between the branches without
twining; but when, according to Dutrochet (tom. xix. p. 299), it
grows near a thin and flexible support, such as the stem of a nettle,
it twines round it. I placed sticks round several plants, and
vertically stretched strings close to others, and the strings alone
were ascended by twining. The stem twines indifferently to the right
or left. Some others species of Solanum, and of another genus, viz.
Habrothamnus, belonging to the same family, are described in
horticultural works as twining plants, but they seem to possess this
faculty in a very feeble degree. We may suspect that the species of
these two genera have as yet only partially acquired the habit of
twining. On the other hand with Tecoma radicans, a member of a
family abounding with twiners and tendril-bearers, but which climbs,
like the ivy, by the aid of rootlets, we may suspect that a former
habit of twining has been lost, for the stem exhibited slight
irregular movements which could hardly be accounted for by changes in
the action of the light. There is no difficulty in understanding how
a spirally twining plant could graduate into a simple root-climber;