Tropical Forests 



east coast of America have been carried right across the 

 Atlantic to the West African shore, for there are two 

 distinct mangrove associations. One occupies the shores 

 of the Pacific and Indian Ocean, and the other occurs on 

 both sides of the Atlantic. 



But where mangroves have established themselves, 

 they are of very great importance as land-formers. Mud- 

 and sand-banks are first colonised by Rhizophora or 

 Brugueira, whose seedlings can also float for a long 

 time (117 days). Then the other mangroves assist to 

 form the usual swamp, with its " dense dark wall of 

 foliage, from which the light is reflected." 4 



As time goes on, the mangrove pioneers are always 

 annexing new territory from the sea, whilst further in- 

 land the level of the mud is slowly rising by the regular 

 deposits at every tide. When the salt-water no longer 

 reaches their roots with every tide, the mangroves 

 begin to be unhealthy and give place to other trees and 

 shrubs. 



Whether this is because the mangroves require a daily 

 salt-bath for health, or because they cannot compete with 

 these plants of ordinary soil, does not seem to be quite 

 understood. 



The first invaders of the mangroves are for the most 

 part certain special transitional forms of trees, shrubs, 

 and climbing plants. 



Their reign is, however, soon terminated by the in- 

 vasion of the tropical forest, which in the end covers 

 with dense jungle what was once estuarine mud, and 

 which may be cleared away for oil-palms, for rice-fields, 

 or other valuable plantations. 



1 Von Faber. 2 Ule, Spruce. 8 Gadow. * Von Faber. 



6 Vaughan-Cornish. 6 Cantlie. 7 Colonial Reports Misc., No. 51. 



8 Schimper, Guppy. See also Engler. 



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