CLIMBING PLANTS. 
215 
is worth, inquiring further into, both as regards the way in 
which the movement is produced, and as to how it can be of 
any service to the plant. Questions are often asked in garden- 
ing periodicals as to how hops or other climbing plants always 
manage to grow precisely in the direction in which they will find 
a support. This fact has surprised many observers, who have 
supposed that climbing plants have some occult sense by which 
they discover the w T hereabouts of the stick, up which they subse- 
quently climb. But there is in reality no kind of mystery in 
the matter : the growing shoot simply goes swinging round till 
it meets with a stick, and then it climbs up it. Now a revolv- 
ing shoot may be more than two feet long, so that it might be 
detained in its swinging-round movements by a stick fixed into 
the ground at a distance of nearly two feet. There would then 
be a straight bit of stem leading from the roots of the plant, 
in a straight line to the stick up which it twines, so that an 
observer who knew nothing of the swinging-round movement 
might be pardoned for supposing that the plant had in some 
way perceived the stick and grown straight at it. This same 
power of swinging round slowly comes into play in the very act 
of climbing up a stick. 
Suppose I take a rope and swing it round my head : that 
may be taken to represent the revolving of the young hop-shoot. 
If, now, I allow it to strike against a rod, the end of the rope 
which projects beyond the rod curls freely round it in a spiral. 
And this may be taken as a rough representation of what a 
climbing plant does when it meets a stick placed in its way. 
That is to say, the part of the shoot which projects beyond the 
stick continues to curl inwards till it comes against the stick ; 
and as growth goes on, the piece of stem which is projecting 
is, of course, all the while getting longer and longer ; and as 
it is continually trying to keep up the swinging-round move- 
ment, it manages to curl round the stick. But there is a 
difference between the rope and the plant in this ; that the 
rope curls round the stick at the same level as that at which 
it is swung, so that if it moves round in a horizontal plane at 
a uniform height above ground, it will curl round the stick at 
that level, and thus will not climb up the stick it strikes against. 
But the climbing plant, although it may swing round when 
searching for a stick, at a fairly uniform level, yet when it 
curls round a stick, does not retain a uniform distance from 
the ground, but by winding round like a corkscrew it gets 
higher and higher at each turn. 
One may find a further illustration of the action of twining 
in the swinging-rope model. It is a peculiarity of twining plants 
that they can only ascend moderately thin supports. A scarlet- 
runner can climb up a bit of string, or a thin stick, an inch or 
