move; they can support themselves, and nothing superfluous is
granted.

A greater number of twiners revolve in a course opposed to that of
the sun, or to the hands of a watch, than in the reversed course,
and, consequently, the majority, as is well known, ascend their
supports from left to right. Occasionally, though rarely, plants of
the same order twine in opposite directions, of which Mohl (p. 125)
gives a case in the Leguminosae, and we have in the table another in
the Acanthaceae. I have seen no instance of two species of the same
genus twining in opposite directions, and such cases must be rare;
but Fritz Muller {16} states that although Mikania scandens twines,
as I have described, from left to right, another species in South
Brazil twines in an opposite direction. It would have been an
anomalous circumstance if no such cases had occurred, for different
individuals of the same species, namely, of Solanum dulcamara
(Dutrochet, tom. xix. p. 299), revolve and twine in two directions:
this plant, however; is a most feeble twiner. Loasa aurantiaca
(Leon, p. 351) offers a much more curious case: I raised seventeen
plants: of these eight revolved in opposition to the sun and
ascended from left to right; five followed the sun and ascended from
right to left; and four revolved and twined first in one direction,
and then reversed their course, {17} the petioles of the opposite
leaves affording a point d'appui for the reversal of the spire. One
of these four plants made seven spiral turns from right to left, and
five turns from left to right. Another plant in the same family, the
Scyphanthus elegans, habitually twines in this same manner. I raised
many plants of it, and the stems of all took one turn, or
occasionally two or even three turns in one direction, and then,
ascending for a short space straight, reversed their course and took