CHAP, xciii EVERGREEN DICOTYLOUS FOREST 347 



ASSOCIATIONS 



Associations formed by single dominant species are exceedingly rare 

 in tropical forest. Owing to the profuse admixture of species tropical 

 rain-forest over the whole world seems to constitute only a single compre- 

 hensive community. In different regions rain-forest is represented b\' 

 different types, which may perhaps be regarded as sub-formations. For 

 instance, there are rain-forests with but little underwood, and others 

 with abundant underwood. Sometimes lianes are scanty, at other times 

 abundant, and the same is true of epiphytes. Huber,^ dealing with 

 Amazonian forests, has shown that detailed examination results in the 

 recognition of distinct associations and varieties of association.- 



APPEXDIX. PALM-FOREST 



In tropical South America one encounters certain forests that are 

 composed mainly of palms and occur on the river-banks or on still moister 

 soil. Thus in Brazil there are the ' buritysales ', that is to say, forests 

 formed by the burity-palms, Mauritia vinifera and M. flexuosa. Lund^ 

 describes these forests in the following w^ords : ' The valleys are clothed 

 with a fresh, luxuriant carpet of grass, and at the bottom, where a stream 

 always flows, they are adorned with groups of the incomparably beau- 

 tiful burity[-palm] ' ; Martius in his ' Tabulae ' figures forests com- 

 posed of both species. Gran Chaco, in north-western Argentina, includes 

 vast plains clothed witli palm-forest composed of Copemicia cerifera. 

 This palm is a light-demanding tree that can form only open and shade- 

 less forests, which are therefore well lighted and presumably have a rich 

 vegetation on the ground. These palm-forests perhaps belong rather to 

 savannah-forest than to rain-forest. 



' J. Huber, 1906. 



" In regard to tropical rain-forest in general, readers should consult the woi'ks 

 of Haberlandt, 1893 ; Schimper, 1S9S ; Whitford, 1906; and Koorders, 1907. 

 " Lund, see Warming, 1892. 



