CLIMBING PLANTS. 



681 



cannot stand the severe strain involved — a strain which must occur whenever 

 the tree, around whose trunk a perennial twiner has wound, increases much in 

 thickness. The twining stems of the Lonicera, figured on p. 160, certainly do 

 not increase in length after lignifying, and must, therefore, act as constricting 

 coils on the young actively-thickening tree-stems, which they often strancrle to 



i?'ig. 159. — Palm-Stem used as a support by the lattice-forming stems of one of the Clusiacese {Fragtosa obovata). 



death. Sometimes one finds the hard basal parts of a liane stem twisted and 

 coiled apparently around nothing. This is due to the fact that the original 

 support has been killed, and then slowly rotting into dust, has been denuded 

 away by the wind and rain. Thus many a liane of the tropical forest seems 

 to have made use, when young, of some living plant with a fairly thick erect 

 stem as its first support, up which it has climbed into the crowns of higher trees. 



