60 A NATURALIST IN THE PACIFIC CH. vn 



Pacific, which [are known to owe their wide distribution in 

 tropical regions to the currents. 



(2) The meagreness of the littoral flora is intensified by the 

 tendency of some of the plants to extend inland and to desert the 

 coasts, and by the occurrence on the beaches of peculiar species 

 not found outside the Hawaiian Islands. 



(3) The absence of the mangrove formation and of so many of 

 the typical beach trees of the Pacific cannot be attributed either to 

 the lack of suitable stations, or to climatic conditions, or to deficient 

 floating power of the seed or fruit. 



(4) As in the case of Tahiti, the mangroves and their associated 

 plants are lacking because the floating seedlings of Rhizophora 

 and Bruguiera, the pioneer plants of a mangrove-swamp, have 

 failed to reach Hawaii in a fit condition for establishing themselves. 

 The numerous plants that accompany a mangrove-swamp have 

 thus been unable to find a home, though the buoyant powers of 

 their fruits or seeds are often great. 



(5 ) With the missing beach-trees, however, which possess fruits 

 that can float for years unharmed in sea-water, no such incapacity 

 is suggested. Most of them have large fruits, which could only 

 reach Hawaii through the currents. This absence from the Hawaiian 

 indigenous strand-plants of most, if not all, of the large-fruited 

 species, where on account of size the agency of birds is absolutely 

 excluded, is very remarkable ; and it at first seems to throw grave 

 suspicion on the efficacy of the currents for the whole strand-flora. 



(6) It is, however, to be noticed that these large-fruited beach 

 trees have not only failed to reach Hawaii but have also failed to 

 reach America. The question thus acquires quite a different aspect, 

 and America becomes the possible source of most of the Hawaiian 

 plants with buoyant seeds or fruits. 



(7) This subject is discussed in the next chapter ; but it is here 

 shown that at their best the currents have taken but a secondary 

 part in stocking the Hawaiian beaches with their plants, since 

 many of the plants have non-buoyant seeds or fruits. 



(8) The drift stranded on the shores of the Hawaiian Islands is 

 composed of logs from the north-west coast of North America. No 

 drift from the south has been discovered ; but it is not unlikely 

 that future investigators will find some seed-drift from tropical 

 America. 



