CHAr. IV] TROPICAL DISTRICTS CONSTANTLY MOIST 321 



so that the epiphyte, though placed high up on a tree, yet resembles a 

 terrestrial plant in regard to its absorption of nutriment. Many epiphytes 

 of this class, like Carludovica Plumieri, which has already been described, 

 and several Araceae are at the same time lianes ; on the other hand, there 

 are also lianes that germinate in the soil, but their stems gradually die 

 from below upwards, so that in their later stages they subsist just like 

 hemi-epiphytes. They have been termed pseudo-epiphytes. 



The largest of the hemi-epiphytes in the tropics of both hemispheres are 

 species of the genus Ficus. The gigantic banyan-tree, Ficus bengalensis 



Fig. 161. Dendrobhim nobile. Transverse section through the aerial root, vl velamen; 

 ee exodermis ; f passage-cells in the exodermis ; c cortex ; ei endodermis ; p pericycle ; s xylem ; 

 :■ phloem ; in pith. Magnified 28. After Strasburger. 



(Fig. 162), of the East Indies is universally known as an immense living 

 columned hall, consisting of a flat expanded canopy of leaves and numerous 

 stem-like prop-roots growing down from the boughs. Like all hemi- 

 epiphytes, the banyan germinates on the bough of a tree, and at first 

 has only such nutritive substances available as occur on the bark of the 

 supporting branch. When once, however, its absorbing-roots are de- 

 veloped 1 3 the supporting tree soon perishes under the shade of its rapidly 

 growing guest, so that but for the knowledge of the development of the 

 banyan the former presence of its host would never be conjectured. 



1 See p. 314. 

 V 



