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considerably more material by its method of climbing by 
twining round a stick, instead of going straight up, supported 
by its tendrils, like the pea. There are several other ways, 
in which climbing by tendrils is a much better plan than 
twining. It is a safer method, as any one may convince him- 
self by comparing the security of a tendril-bearer in a heavy 
wind, with the ease with which a twiner is partly blown from 
its support. Again, by looking at those leaf-climbing plants 
which still possess in addition the power of twining, it will be 
seen how incomparably better they grasp a stick than does a 
simple twiner. And again, a twiner from being best fitted to 
climb bare stems often has to start in the shade, whereas a leaf 
or tendril climber can ramble for the whole extent of its 
growth up the sunny side of a bush. 
We can thus see plainly how it has been an advantage for 
twining plants to develope into leaf-climbers. We shall also 
find reasons why a leaf-climber should find it advantageous to 
become a tendril-climber. 
We have seen how tendrils form a more sensitive, efficient 
grasping organ, than simple leaves. Tendrils possess also the 
valuable power of shortening themselves by spirally contract- 
ing, and thus pulling up after them the stem on which they 
grow ; and afterwards serving as springs and breaking the force 
of the wind. We have had some cases where we see the close 
relationship between leaf and tendril-climbers, and where we 
can see intermediate stages in the process of transition from 
one method of climbing to the other. 
In certain kinds of Fumaria we can follow the whole pro- 
cess. Thus we have one kind, which is a pure leaf-climber, 
grasping by its leaf-stalks, which bear leaflets not at all re- 
duced in size. A second genus has the end leaflets very much 
smaller than the rest. A third kind has the leaflets reduced to 
microscopical dimensions ; and lastly, a fourth kind has true 
and perfect tendrils. If we could see the ancestors of this 
last kind we should undoubtedly have a series of forms con- 
necting it with an extinct leaf-climber, resembling the series 
which at present connects it with its contemporary leaf-climbing 
relatives. 
To repeat once more the steps which it is believed have 
occurred in the evolution of climbing plants. It is probable 
that plants have become twiners by exaggerating a swinging- 
round or revolving movement, which occurred in a rudimentary 
form, and in a useless condition, in some of their ancestors. 
This movement has been utilized for twining, the stimulus 
which has driven the process of change in this direction having 
been the necessity for light. 
The second stage has been the development of sensitive 
