14] VEGETATIONAL TYPES OF TROPICAL LANDS 431 



them the cHmbers or ' vines ' are generally the most important. 

 Indeed the woody climbers, also called lianes (or lianas), are apt to 

 be so large and numerous as to afford one of the most impressive 

 features of the tropical rain forest. They may be thin and wire- 

 like or rope-like, or as thick as a man's thigh, vanishing like cables 

 into the mass of foliage overhead, or here and there hanging down 

 in gigantic loops. Often they are unbranched up to the profusely 

 branched crown. Some are said to attain lengths of over 200 metres, 

 ascending one tree, then descending to the ground before ascending 

 another, and so on. Often they pass from tree to tree and link 

 the crowns so firmly that even if a tree is cut through at the base 

 it will not fall. 



Lianes are most abundant where the forest has been disturbed, 

 or about its margins — as for example along river banks where they 

 may completely screen the interior of the forest. In addition to 

 the large woody climbers that reach the crowns particularly of the 

 B stratum of trees, there are usually some small, mainly herbaceous 

 ones (including Ferns) that seldom emerge from the shade of the 

 undergrowth. Among the climbers the large lianes comprise, how- 

 ever, by far the more numerous synusiae (groups of plants of similar 

 life-form, each filling much the same ecological niche and playing 

 a similar role, and contributing to a biocoenosis — cf. p. 321). These 

 large lianes belong to many different families and genera — chiefly 

 of dicotyledons, though Climbing Palms or Rattans are often 

 prominent among them. 



The climbers as a whole include twiners which by the revolving 

 movement of their growing tips become wound around their sup- 

 ports ; also root-climbers and tendril-climbers which have specialized 

 sensitive roots and tendrils, respectively, for attachment ; and 

 scramblers which lack such abilities or organs but scramble over 

 other plants, often being aided passively in their climbing by 

 recurved spines or wide branching. Many species use more than 

 one method. As the crowns of tropical trees tend to be less branched 

 and less leafy than those of temperate trees of similar size, woody 

 climbers help to close the canopy and decrease the penetration of 

 light. They may also mis-shape the crowns or constrict the stems 

 of trees, though such things are more regularly done by stranglers 

 {see pp. 435-6). 



4. Epiphytes. These are plants which grow attached to the trunks, 

 branches, and even living leaves of the trees, shrubs, and lianes, 

 such situations being the only ones available in closed forests for 



