442 A NATURALIST IN THE PACIFIC chap. 



inland regions than of the coast swamps, and we have before 

 observed that they failed to record Scirpodendron costatum, a 

 giant-sedge very common and conspicuous in the swamps. It is 

 not easy to understand Dr. Seemann's remark that " mangroves 

 are restricted to but few parts of the larger islands." Home, who 

 was in the islands eighteen years afterwards, makes frequent 

 allusion to them. The natives whom I questioned closely on this 

 subject scouted the idea that any of the four mangroves above 

 named were recent arrivals. The coasts, as they said, had always 

 been extensively fringed by mangroves ; and the reader has only 

 to refer to my remarks in the second chapter of my volume on the 

 geology of Vanua Levu to convince himself that mangrove swamps 

 of considerable extent existed in the time of Commodore Wilkes 

 (1840). 



The Relative Abundance and Mode of Associatio7i of the three 



Fijian forms of RhizopJiora. 



Stated in their order of frequency, we have first Rhizophora 

 mangle, the American species, then Rhizophora mucronata, the 

 Asiatic species, and lastly the Selala. The first is equally at 

 home at the sea-border and on the banks of brackish estuaries. 

 The second is, as a rule, more exclusively at home on the sea- 

 coasts ; and the same may be said for the Selala. Usually all 

 three kinds occur in the lower part of an estuary ; but as we ascend 

 the river and the water freshens, the Asiatic Rhizophora and the 

 Selala disappear, and the American plant is alone found in the 

 higher reaches, where the density of the water ranges according to 

 the state of the tide between I'ooo and roio. I examined the 

 distribution of these three forms of Rhizophora in numerous 

 estuaries of Vanua Levu, as well as in the Rewa estuary in Viti 

 Levu ; and it was ascertained that in all cases they followed the 

 rule above indicated. When the estuary receives but few streams 

 and the water is mostly salt, the three Rhizophoras may extend 

 miles inland ; but when it contains a large body of fresh-water, 

 Rhizophora mangle may be the only form observed from the mouth 

 of the river to the head of the estuary, and it may monopolise the 

 adjacent coasts. On the other hand, Rhizophora mucronata may 

 occupy almost exclusively a long extent of coast ; or the Selala 

 may prevail in certain localities, as on parts of the Mathuata coast 

 of Vanua Levu. 



The manner of association of these three Rhizophoras is of 



