478 



ZONES AND REGIONS 



[Pt. Ill, Sect. II 



with the tropical rain-forest in the great multiplicity of its species of trees ; 

 but a single dominant species, or a dominant group of allied species, is much 



commoner in the temperate rain-forest than in the tropical. Thus, species 

 of oak or beech readily grow in it as social trees. Temperate and tropical 

 forms are intermingled ; the tropical forms being naturally more numerous 



