406 



ZONES AND REGIONS 



[Pt. Ill, Sect. I 



are largely fringed with a short-stemmed palm, Nipa fruticans (Figs. 226 

 and 227), which occasionally, for instance in Sumatra, alone covers exten- 

 sive tracts. This variety of mangrove is best distinguished from the true 

 mangrove formation as Nipa-formation. Rhizophoraceae hardly ever occur 

 in the Nipa-formation, but a few other mangrove trees, such as Avicennia 

 officinalis, Sonneratia acida, sometimes appear, and very frequently the fern 

 Chrysodium aureum. 



Behind the mangrove and Nipa-formation, the land, becoming gradually 

 drier and being free from regular inundation by the tide, shows an increas- 



Fig. 227. From the Javanese mangrove. In front: Rhizophora mucronata, bearing seedlings. In 

 the background : Nipa fruticans (Nipa-formation). From a photograph by G. Karsten. 



ing number of species belonging to drier saline soil, Hibiscus tiliaceus 

 mixed with Chrysodium aureum being specially abundant (Fig. 228). 



The Western Mangrove. 



The western mangrove greatly resembles the eastern in its oecological 

 character, but is much poorer in species and much less richly differentiated. 

 It contains four species only : — • 



Rhizophoraceae: Rhizophora Mangle, Linn. Combrctaccae : Laguncu- 

 laria racemosa, Gartn. Verbenaceae\ Avicennia tomentosa, Jacq., and 

 A. nitida, Jacq. 



The West African mangrove appears to be without Avicennia tomentosa. 



