These facts are remarkable; for there can hardly be
a doubt that in the dryer provinces of South Africa these plants have
propagated themselves for thousands of generations in an erect
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.
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