A NATURALIST IN BRAZIL 



climbing-irons; others coil themselves, even before they seize their 

 support, into an elastic spiral, Hke a clock-spring; others develop 

 spatulate "suckers," which enable the creepers to scale bare walls. 

 Many tendrils grow considerably thicker once they have slung 

 themselves round a supporting bough, and are consequently more 

 difficult to dislodge. 



• • • • « 



The stems of the lianas have also undergone extensive modifica- 

 tions in adaptation to their mode of life. When the wind blows the 

 boughs which support them apart they must be able to resist a 

 violent pull, and when they hang from the boughs overhead, or are 

 slung from tree to tree in long festoons, they must be able to bear 

 their own weight. One may seat oneself in such a rustic trapeze 

 and swing to and fro. In order that the lianas may be able to give 

 to a pull, they are often spirally coiled at the points of their attach- 

 ments to the boughs, so that they can be drawn out Uke springs, 

 contracting when the pull is diminished. 



The stem of the liana is of a peculiar structure. It is frequently 

 twisted like a cable ; sometimes it is flat like a ribbon, as in some of 

 the Brazilian Bauhinias (Fig. 5). These ribbon-like stems apply 

 themselves closely to the supporting tree, but at the same time they 

 twist themselves spirally or contract into undulations, giving rise to 

 the remarkable formations known as "monkey-ladders." These 

 modifications are possible because the lianas have not, like trees, a 

 homogeneous woody structure enclosed by a circular sheath of bast 

 and bark, the stem being built up of several woody structures, which 

 are capable of shifting their respective positions. The structure of the 

 liana is thus not unlike that of a cable. 



The growth of the liana is not foreordained, like that of a tree, 

 which grows permanently in one position, building itself up in its 

 own characteristic fashion; for the tree supporting the liana grows 

 upwards, and the creeper has to follow; the older it grows the 

 heavier it becomes, until at last the massive stem can no longer 

 support itself, and the older climbing-organs no longer fulfil their 

 function, and one day the stem slips and slides downwards. Part of 

 it may perhaps remain hanging from a crotch of the supporting 

 tree ; the rest collapses on to the ground. Since this process is repeated 

 again and again, the elastic stem is eventually coiled into a serpentine 

 tangle. When one sees the stem of a liana swaying above the ground, 

 suspended by long cables from the topmost branches, one wonders 

 how these living cables could possibly have reached the position 

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