THE LIANAS 



spectacle is most fascinating; the boundary between animal and 

 vegetable life seems abolished. 



But what an impressive spectacle would be afforded if a photo- 

 grapher were to make such chain-exposures in a tropical forest and 

 then, by projecting the film, speed up the rate of growth ! Since in 

 many of the tropical plants the diameter of the circles described by 

 the tips of the shoots may be as much as six feet, one would see long 

 tentacles emerging here and there from the undergrowth, groping 

 about in uncanny silence until they found their victim, and seizing 

 it in their enduring embrace. 



The most highly-organized lianas are those which do not enlace 

 the tree-trunks with their shoots, but have developed special tendrils, 

 which circle round in search of a support. 

 These delicate, slender and elastic structures 

 are so irritable that everything touched by 

 them is at once embraced and held fast (Fig. 5) . 

 After a time that part of the tendril which lies 

 between the tree and the liana contracts into 

 a corkscrew form, drawing the plant after it, 

 so that the latter is suspended as by a spiral 

 spring. 



Since the tendril is a specialized organ, 

 serving an exclusive purpose, it is not sur- 

 prising that it should do its work more rapidly 

 than the shoots of the twining lianas. Many 

 tendrils rotate through a complete circle in as 

 brief a period as 25 minutes, and the tip of 

 the tendril begins to curve within twenty 

 seconds of touching a bough, so that in four 

 minutes the first complete noose is thrown round the support. 

 There are other plants, of course, whose tendrils are more deliberate. 

 But the enlacement of the supporting tree-trunk or bough is effected 

 more rapidly and completely by such plants as are equipped with 

 tendrils. They pass easily from bough to bough, and form a regular 

 overgrowth on the tree-tops ; their shoots hang down into the trees, 

 and seize upon fresh points of support, until at last a whole group 

 of trees may seem to be swathed in a green foam, or ceilings and 

 arbours of foliage spring into being. It is on the edge of the forest 

 that such a spectacle is most frequent. 



Tendrils may be evolved from any part of the plant ; the mid-rib, 

 the leaf-stalks, the bracts, or what not. Many tendrils become 



95 



Fig. 5. — Section of stem 

 of a Bauhinia, with 

 leaf and tendril. (After 

 Kerner Hansen) 



