m.; and this represents fairly well the usual rate, taking quick and
slow movers, amongst phanerogamic plants. The rate was accelerated
by increased temperature. At each stage of growth only the two upper
internodes revolved. A line painted along the convex surface of a
revolving internode becomes first lateral, then concave, then lateral
and ultimately again convex. Neither the internodes nor the petioles
are irritable when rubbed. The movement is in the usual direction,
namely, in opposition to the course of the sun; and when the stem
twines round a thin stick, it becomes twisted on its own axis in the
same direction. After the young internodes have twined round a
stick, their continued growth causes them to slip a little upwards.
If the stick be soon removed, they straighten themselves, and
recommence revolving. The extremities of the depending shoots turn
upwards, and twine on themselves. In all these respects we have
complete identity with twining phanerogamic plants; and the above
enumeration may serve as a summary of the leading characteristics of
all twining plants.

The power of revolving depends on the general health and vigour of
the plant, as has been laboriously shown by Palm. But the movement
of each separate internode is so independent of the others, that
cutting off an upper one does not affect the revolutions of a lower
one. When, however, Dutrochet cut off two whole shoots of the Hop,
and placed them in water, the movement was greatly retarded; for one
revolved in 20 hrs. and the other in 23 hrs., whereas they ought to
have revolved in between 2 hrs. and 2 hrs. 30 m. Shoots of the
Kidney-bean, cut off and placed in water, were similarly retarded,
but in a less degree. I have repeatedly observed that carrying a
plant from the greenhouse to my room, or from one part to another of
the greenhouse, always stopped the movement for a time; hence I