CHAP, xciii EVERGREEN DICOTYLOUS FOREST 341 



America), the cactaceous Rhipsalis (in America and Africa), and other 

 spermophytic famihes, as well as ferns, mosses, and so forth. Trees of 

 the forests situate in the cloud-belt in Java and the Moluccas are en- 

 veloped in a soaking mossy felt, which may be thicker than the trunks 

 themselves and imparts to them a peculiar, dark appearance. Here, too, 

 lies the proper home of the Hymenophyllaceae, ferns whose anatomical 

 structure reveals them as true ' mist -plants '. Even the leaves of ever- 

 green species may be densely clothed with epiphyllous algae, liverworts, 

 and small lichens. Among the plants requiring the heaviest rainfall,, 

 according to Schimper,^ we may regard woody epiphytes, of which many 

 develop in rainy primeval forests. The fiery Rhododendron javanicum 

 decks the tree-crowns in mountain-forests of Java, and together with it 

 one sees species of Ficus, of the melastomaceous Medinilla, of the loga- 

 niaceous Fagraea, and of the araliaceous Sciadophyllum. In Javanese 

 mountain-forests one commonly encounters the huge epiphytic ferns 

 Asplenium Nidus and Platycerium alcicorne ; large specimens of Lyco- 

 podium Phlegmaria and other species of Lycopodium, also of Psilotum 

 flaccidum, which hang loosely down from the trees in wisps, like so many 

 horsetails. Finally, there is a wealth of lianes, whose iiowers and fruits 

 one can rarely see, and whose long, often curiously shaped stems span the 

 distance between soil and tree-crowns, or hang down from the latter or 

 partly trail along the ground. Many plants in addition to trees provide 

 innumerable points of support, enabling Hanes to reach the tree-crowns. 

 The amount of light prevailing in the forest accounts for the luxuriant 

 \'egetation ; light can pass through the open crowns of the topmost storey 

 <m to the lower crowns, and downwards through these. The twilight 

 prevailing is much less dark than in European beech-forest. All the 

 species, as Junghuhn - expresses it, seem to ' abhor a vacuum ' and to 

 combine in an endeavour to utilize all the space available. 



Number of species. The number of species in tropical rain-forest is 

 extraordinarily large. The absence of any social method of growth on 

 the part of species has often been mentioned by writers, and provides 

 a sharp contrast to the uniformity of forest in northern Europe. This 

 IS well illustrated by the fact that in Brazil, on three geographical square 

 miles round Lagoa Santa, there are about 400 species of trees in the forest ^ ; 

 cilso by the fact mentioned by Whitford "* that in the Phihppines, on an 

 area of 1,200 square metres, there grew 896 trees exceeding 3 metres in 

 height and belonging to 120 species. This multiplicity of species is partly 

 due to a geological cause, namely, the antiquity and uninterrupted de- 

 velopment of tropical life ^ : but it is also due to a physical cause, 

 namely, favourable hfe-conditions ; for there are examples showing that a 

 moist, rich soil entertains a larger number of species than does adjoining 

 dry soil (forest and campos of Brazil).^ It seems to be justifiable to assume 

 that the rate of production of new species is, in general, dependent upon 

 favourable conditions of life, and that it is therefore greater in tropical 

 than in cold or temperate lands. 



' Schimper, 1898. ' Junghuhn, 1853-4. * Warming, 1892. 



Whitford, 1906. ' Wallace, 1891 ; W'arming, 1890. * Warming, 1892. 



