THE STEM OT 
sufficient speed, a trunk that shall be self-supporting 
and at the same time lift its leaves to the light above. 
Climbing plants, by relying on others for support, and 
thus reducing the expenditure of material and energy 
necessary for the production of an independent stem, 
have solved the problem. They increase in length 
without increasing much in girth, and so, soon lift 
their leaves above the tops of the forest trees. Different 
plants have solved the problem in different ways, and 
it would seem that every suitable variation, whether 
of leaf, root, or stem, has been taken advantage of to 
get the leaves quickly to the light. The supplejack 
loops and twists itself round the branches of the trees, 
and when provided with suitable support, behaves not 
unlike the twining stems of the hop and convolvulus. 
It will be noted that, while the twining of the hop 
(Fig. 61) is always clockwise, that of the convolvulus 
(Fig. 62) and scarlet runner is always anti-clockwise. 
The kie-kie and several rata vines fix aérial roots into 
crevices in the bark of trees and thus pull themselves 
up in much the same way as the ivy. The clematis 
(Fig. 63) climbs by twisting its leaf petioles round 
twigs and other adjacent objects, as also does the white 
climbing nightshade. The New Zealand bramble or 
lawyer (Fig. 64), like its European relative, scrambles 
by means of curved hooks set chiefly under the petioles 
and along the midribs of the leaves, over the under- 
growth and small trees on the verge of the forest. <A 
eurious development is seen in the eleagnus, in which 
the branches near the ends of the shoots bend back to 
form a kind of crook by which the plant may lift itself. 
As new branches arise nearer the tip, and those first 
produced are no longer needed for support, the latter 
straighten out and devote themselves to placing the 
leaves in the most favourable position for light. The 
passion flower, a species of which is found in the New 
Zealand forest, the grape vine, the sweet pea, and the 
G 
