46 A NATURALIST IN THE PACIFIC ch. v 



(2) Excluding the mangroves and the plants associated with 

 them in the coast-swamps, there are few littoral plants of the 

 islands of the tropical Pacific that do not extend inland in one 

 region or another. 



(3) The Fijian shore-plants can be rudely arranged in three 

 groups, those of the mangrove-swamp, those of the sandy beach, 

 and those of the intermediate districts, the last including those 

 plants that occur typically at the borders of a mangrove-swamp, 

 though some of them can thrive equally well on a beach. 



(4) There is a law of association connecting many plants with 

 a mangrove-swamp in such a manner that when the true man- 

 groves are not represented in a Polynesian group, as in Tahiti or 

 in Hawaii, the plants in question are also absent, notwithstanding 

 that in many cases, such as those of Clerodendron inerme and 

 Heritiera littoralis, they possess seeds or seedvessels of great 

 floating power. 



(5) The fruits or seeds or seedlings, as the case may be, of the 

 plants of the mangrove-swamp and of the bordering districts float 

 almost without exception for long periods. This is true also of 

 five-sixths of the beach-plants, whilst the remainder owe their 

 dispersal chiefly to birds. 



(6) The small non-buoyant group of the beach-plants repre- 

 sents that portion of the strand-flora that is most likely to be 

 recruited from the inland flora. It is here that exists the zone of 

 change ; and it is in this respect that the littoral floras of the 

 tropics differ principally amongst each other, the recruits from 

 inland varying naturally with the floras of different regions. 



Though it does not come within my plan to discuss the littoral 

 floras of the adjacent smaller groups of Tonga and Samoa, it may 

 be remarked that they reflect most of the principal features of the 

 strand-flora of Fiji. In particular it may be observed that they 

 possess the mangrove-formation, but to a more limited extent. 

 Both own the mangrove genera Rhizophora and Bruguiera, whilst 

 Carapa is also found in Tonga. The intermediate formation is 

 represented in Tonga by Clerodendron inerme, Excaecaria Agal- 

 locha, and Heritiera littoralis ; whilst in Samoa we find, besides 

 the first-named species, Barringtonia racemosa and Scirpodendron 

 costatum. In both the beach-formation is well represented. 



