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OX THE PHENOMENA OF MOTION AND SENSITIVE- 
NESS IN CLIMBING PLANTS. 
BY THE REV. GEORGE HENSLOW, M.A., F.L.S., &c. 
P REVIOUSLY to Mr. Darwin* s elaborate investigations on 
climbing plants, observations bad been made by Palm, 
Mohl, Professor Asa Gray, and others ; but in point of variety 
and novelty many of bis researches far surpass those of 
the latter botanist. A resume of his deeply interesting paper 
in the Journal of the Linnean Society , vol. ix., Nos. 33 and 
34, we purpose submitting to the readers of the Popular 
Science Review. 
Mr. Darwin commences by observing that climbing plants 
may be conveniently divided into four classes ; namely, those 
which twine spirally round a support (spirally twining plants),' 
those which ascend by the movements of the foot- stalks or 
tips of their leaves (leaf climbers), those which ascend by true 
tendrils (tendril bearers), and, lastly, those which are famished 
with hooks or rootlets (hook and root climbers) . 
I. Spirally Twining Plants. — This is the largest class, and 
they apparently indicate the simplest or primordial condition. 
The first example is that of the hop, the movement of which 
Mr. Darwin thus describes : — 
“When the shoot of a hop (Humulus lupulus ) rises from the ground,, 
the two or three first-formed internodes are straight, and remain stationary ; 
but the next formed, whilst very young, may be seen to bend to one side,, 
and to travel slowly round towards all points of the compass, moving, like 
the hands of a watch, with the sun. . . . The average rate was 2h. 8m. 
for each revolution. . . . Each separate internode, as it grows old, 
ceases to revolve, becoming upright and rigid. . . . Generally, three 
internodes revolve simultaneously ; with all the plants observed, if in full 
health, two revolved ; so that by the time one had ceased that above it was 
in full action, with a terminal internode first commencing to revolve.” 
A point connected with this revolving motion, but not the 
cause of it, is that the axis of each internode becomes twisted 
as the plant continues to grow and as each internode 
assumes a rigid form ; thus the first internode of the hop 
