XVI LITTORAL AND INLAND PLANTS' RELATIONSHIP 167 



together, the beach flora presents itself in the Pacific as practically- 

 independent of the inland flora as regards its origin. It has 

 received in these regions but few recruits from inland. It has 

 yielded, except in Hawaii, but few recruits to the inland flora. In 

 this ocean it bears the stamp of a high antiquity, though in the 

 mass no doubt of more recent origin than the mangrove flora. 



Yet, as I have remarked in different parts of this work, even 

 with the beach genera possessing no inland species, considerable 

 variety is displayed in the behaviour of the strand species. Thus, 

 whilst some, like Pemphis acidula, Tournefortia argentea, and 

 Triumfetta procumbens, rarely if ever leave the beach, others, like 

 Heritiera littoralis and Excsecaria agallocha, find a home on the 

 borders of the mangrove swamps, and one or two extend inland 

 and take their place in the forests, either as trees (Afzel'a bijuga) 

 or as giant climbers (Entada scandens). Others again, like 

 Cassytha filiformis, Cerbera Odollam, and Cycas circinalis, with a 

 number of other beach-plants, may invade the interior of the island 

 wherever arid plains or exposed scantily wooded districts offer 

 conditions conformable to the xerophytic habit of the beach-plants. 



It will thus be perceived that although the inland and coast 

 floras of an island are in the mass distinct, the line of separation is 

 by no means always well defined. Beach-plants are something 

 more than salt-lovers in their ways. They are in the first place 

 xerophilous, or, in other words, they will be equally at home in 

 exposed situations away from the coast where the soil is dry and 

 the rainfall scanty. Whenev^er these conditions are presented by 

 the districts backing the coast, as we find for instance in the plains 

 on the lee or dry sides of many a Pacific island, the shore-plants 

 will often leave the beach and travel far inland. 



Summary 0^ Chapters XIV., X V., XV I. 



(i) Though littoral floras are as a rule chiefly made up of 

 two sets of plants, one brought through the agency of the currents 

 from regions outside, and the other derived from the inland flora 

 of the region concerned, the proportion of the two varies much 

 amongst temperate and tropical strand-floras, the current-borne 

 plants forming the majority in the tropics, and those from the 

 inland flora of the region prevailing in the temperate zone. 



(2) There is, therefore, far greater uniformity as a rule amongst 

 tropical strand-floras than in the temperate zone, since in temperate 

 latitudes the prevailing constituents of the strand flora vary with 



