CHAPTER IV 

 TROPICAL DISTRICTS CONSTANTLY MOIST 



i. Distribution of the Tropical Rain-Forest. 2. General Character of the 

 Tropical Rain-Forest, i. External Aspect of the Forest. Surface and profile, 

 ii. Interior of the Forest. Variable density. Frequent and widespread constituents of 

 the flora. Woody plants. Herbs. Lianes. Epiphytes. The struggle for light. Atmo- 

 spheric humidity, iii. Tropical Rain-Forest in Asia. Vegetation and flora on the Gedeh 

 and Salak in Java. Characteristic forms. Occurrence of brightly-coloured flowers. 

 Rain-forest in Pegu, according to F. Kurz. iv. Tropical Rain-Forest in Africa. The 

 forest of the Loango coast according to Pechuel-Losche. Rain-forest in Usambara. 

 v. Tropical Rain-Forest in America. vi. Tropical Rain-Forest in Australia and 

 Polynesia. 3. Oecological Characteristics of Plants growing in the Rain-Forest. 

 i. Trees and Shrubs of the Rain-Forest. The stems of the trees. Plank-buttresses. 

 Bark. Branching, ii. Terrestrial Herbs oj the Rain-Forest. Coloured foliage. The 

 Hymenophyllaceae. iii. Lianes of the Rain-Forest. Palm-lianes. Scrambling bamboos. 

 Root-climbers. Cyclanthaceae and Pandanaceae. Araceae. Their absorbing and 

 attaching roots. Twiners. Tendrillous plants. Species of Bauhinia with ribbon-shaped, 

 wavy stems, iv. Epiphytes of the Rain-Forest. Occurrence. Subdivision according to 

 their mode of life into Proto-epiphytes, Hemi-epiphytes, Nest-epiphytes, Tank-epiphytes. 

 Characteristics of the groups. Water-reservoirs. Velamen of orchids and aroids. 

 Aphyllous orchids. The banyan. Humus-collecting orchids. Ferns with collecting 

 funnels and with pocket-leaves. Bromeliaceae. Absorption of water through the leaves. 

 Illumination of epiphytes. Epiphylly. Distribution of epiphytes on an individual tree, 

 v. Buds in the Rain-Forest. Unprotected buds. Protective devices of active buds. The 

 sprouting of leaves. Pendent leaves and pendent shoots. Flower-buds under water. 

 Flower-buds with water-calyces, vi. Caiilifloiy in the Rain-Forest. Cauliflory on stem 

 and branches. Aphyllous fertile twigs, vii. Saprophytes and Parasites i?i the Rain-Forest. 

 Plants without chlorophyll belonging to the Orchidaceae, Burmanniaceae, Triuridaceae, 

 Gentianaceae. Balanophoraceae. Rafflesia. Loranthaceae. 



1. DISTRIBUTION OF THE TROPICAL RAIN-FOREST. 



In his map showing the distribution of precipitation according to the 

 seasons, Hann subdivides the tropical zone into districts with a dry season— 

 that is to say, with months in which the normal frequency of rain falls below 

 o-2o, in other words with six rainy days in a month — and into districts 

 without any dry season proper. Districts without any dry season may be 

 described as constantly humid regions. Precipitation in them, however, is 

 not uniform throughout the year, but is distributed over more humid 

 and less humid periods, the alternations of which are not without influence 

 on vegetation, for, as was shown in the previous chapter, this influence 

 frequently makes itself felt, especially as regards the times of flowering. 



