WATER SUPPLY OF EPIPHYTES 



73 



have been evolved in the earth, and that epiphytism has 

 taken advantage of it. 



Collection of Humus. — In a number of epiphytes 

 humus is collected by the plant and forms a substratum 

 into which the roots grow. A good example of one of these 

 " nest epiphytes," as Schimper terms them, is the aroid 

 Anthurium ellipticiim, described by 

 Goebel. A mass of adventitious 

 roots arises near the base of the 

 stem, growing upwards and outwards 

 and forming a massive felt in which 

 humus collects. The West Indian 

 orchid, Oncidiiim altissimutn, has a 

 basket-like network of roots as big 

 as a man's head, in which the rubbish 

 falling from the tree-tops collects. 

 In the Javan orchid Grammato- 

 phyllum speciosum, the root-work 

 surrounds the host tree and may be 

 a couple of yards thick ; Anthurium 

 Hugelii, a West Indian aroid, collects 

 rain and humus in a funnel formed 

 by its leaves, and into this the roots 

 grow. Here may be mentioned the 

 plants restricted to the humus nests 

 formed by some ants in trees of the 

 forests of tropical South America. 



Yet more remarkable is the ar- 

 rangement in Dischidia Rafflesiana, 

 an epiphytic asclepiad of Java (Fig. 

 6). The fleshy leaves arise in pairs, 

 and one develops as a pitcher completely closed except 

 for a narrow opening above. Into this opening grows 

 an adventitious root arising beside the leaf ; inside it 

 branches vigorously and lines the wall with a network of 

 rootlets. Water and fine organic material find their way 

 into the pitcher and supply these roots. In another 

 asclepiad, Conchophyllum imbricatum, the leaves are fleshy, 



Fig. 6. — Leaf-pitcher of 

 Dischidia Rafflesiana ; 

 cut open to show the 

 root system which has 

 grown into it. | nat. 

 size. (After Treub.) 



