247 



the presence of several magnoliaceous trees with beautiful 

 flowers, e.g. Magnolia Campbellii. 



224. These forests are found on (5) Tidal or 



the mud-banks bordering the sea and tidal rivers. The trees Littoral 

 are here never large, and the commonest species are those I 

 usually known collectively as mangroves, whence fhisTtype of 

 forest is often called mangrove-forest. Owing to their peculiar 

 environment, the plants in this class of forest have to contend 

 chiefly with 



(1) The action of the wind, waves, and tides tending to 



uproot the trees growing in the soft mud. 



(2) The excess of salts in the water around the roots. 



(3) The difficulty of obtaining sufficient oxygen for their 



roots. 



(4) The danger of having their seedlings submerged and 



killed by the rising tide. 



We should therefore naturally expect that comparatively 

 few species would *"be able to exist under these unfavourable 

 conditions and that those which are able to survive would 

 possess certain definite and well-marked characteristics. 



In the littoral forests of India and Burma " the species of tree 

 which forms the advanced line along the sea and which, by its 

 slow forward march, causes a gradual elevation of the coast, 

 is Rhizophora mucronata. No mangrove-tree is better equip- 

 ped for resisting the movements of the tide on the soft mud, 

 for propagating itself under these difficult conditions, and 

 for recovering from the frequently quite undilute salt sea- 

 water, the water lost in transpiration. The scaffolding of bow- 

 shaped stilt-roots supporting the stem represents a complete 

 system of anchors, which is strengthened by new roots growing 

 down from the branches to balance the growth of the crown." 

 (In other species of mangrove growing further from the sea 

 these anchoring roots are less strongly developed or are alto- 

 gether absent.) : The leaves possess a marked xerophilous 

 structure with a thick cuticle. protected 



stomata, and especially a large-celled thin- walled aqueous tissue, 

 the dimensions of which increase with the age of the leaf and 

 with the corresponding rise in the amount of salt contained. Old 

 leaves serve essentially as water- reservoirs for the younger 

 leaves."* 



* Schimper op. cit., p. 396. 



