Tropical orchids are mostly epiphytal - that is, they grow upon trees without deriving nourishment from them.
Epiphytal orchids are very frequent, and reach even to 10,000 ft.
They differ from all the forms already noticed in being shrubby and epiphytal in habit, and in having the branches compressed and dilated so as to resemble thick fleshy leaves, with a strong median axis and rounded woody base.
- This name is now restricted to two or three dwarf branching Brazilian epiphytal plants of extreme beauty, which agree with Phyllocactus in having the branches dilated into the form of fleshy leaves, but differ in having them divided into short truncate leaf-like portions, which are articulated, that is to say, provided with a joint by which they separate spontaneously; the margins are crenate or dentate, and the flowers, which are large and showy, magenta or crimson, appear at the apex of the terminal joints.
All the species are epiphytal in habit.
For epiphytal plants like orchids the most thorough drainage must be secured by the abundant use of potsherds, small pots being sometimes inserted inside the larger ones, or by planting in shallow pots or pans, so that there shall be no large mass of soil to get consolidated.
In Sikkim the mountains are covered with dense forest of tall umbrageous trees, commonly accompanied by a luxuriant growth of under shrubs, and adorned with climbing and epiphytal plants in wonderful profusion.
The herbaceous tropical and semi-tropical vegetation likewise by degrees disappears, the Scitamineae, epiphytal and terrestrial Orchideae, Araceae, Cyrtandraceae and Begoniae only occur in small numbers in Kumaon, and scarcely extend west of the Sutlej.
Epiphytal orchids are extremely numerous between 6000 and 8000 ft.