108 PLANT LIFE 
on the development of a correspondingly 
thick trunk. 
But the various exigencies and risks in- 
separable from a climbing habit, have given 
free scope to the play of individual variation 
among the numerous species, both related 
and unrelated to each other, of which the 
great group of the climbers is composed. 
It is this circumstance that gives them their 
special interest, and also renders them so 
instructive. 
Many of the climbers which grow in the 
tropical jungles exhibit extreme specialisation 
in connection with their climbing habits, by 
which they are enabled rapidly to reach the 
leafy canopy of the forest, although this is 
often many feet above the ground. Some- 
times they steal a march on circumstances, as 
it were, and the seed is able to germinate in 
the upper fork of a tree. This occurs in 
many of the large figs, e. g. the India-rubber 
Fig, which, perhaps, can hardly be called 
a climber in the ordinary sense of the term. 
Plants of this kind produce roots which 
rapidly grow downwards and penetrate the 
soil, the young fig securing the great ad- 
vantage that, when its foliage sprouts forth, 
it is very soon fully exposed to light. 
Other climbers behave differently, and 
more nearly resemble the kind of growth of 
an ordinary plant, but with certain significant 
differences. The seed germinates on the 
ground, and the thin shoot, which grows 
