MODES OF CLIMBING 55 
XITI.—MODES OF CLIMBING. 
The stems of many plants are not sufficiently strong to 
enable them to stand erect, and spread out their leaves to 
the light and air. These obtain the support they require 
by leaning against or fixing themselves to other objects. 
Some of the methods adopted to secure suppose will be 
seen by a study of the following :— 
Twining Stems. Twining stems are those which find 
support in twisting round objects that are erect or nearly 
so. The twining takes 
~<L/ place moreover in a defi- 
_ of nite direction. The Con- 
We 
( fe aS/ volvulus, for instance, re- 
Wir volves round the support 
DD from right to left, form- 
r 
ing a left-handed spiral ; 
whereas both the Hop and 
the Honeysuckle revolve 
from left to right, 7.2. ina 
right-handed spiral. 
Root Climbers. The — 
Ivy ascends by means of 
roots, which it developes 
on the shaded side, 7.¢., on 
the side away from the 
Bl Pos eoae s sun. These roots pour 
out a sticky fluid which 
hardens and fixes the plant to the support. 
Tendril Climbers. Many plants, ¢9., Pea, Vine, 
Passion-flower, possess peculiar climbing organs named 
tendrils. On the Pea these occupy relatively the same 
position as the leaflets further down the leaf-stalk. They 
are, in fact, modified leaflets. In the Passion-flower, how- 
ever, the tendrils arise in the axils of the leaves, and hence 
