THE PALAEOTROPICS 255 



Hawaii 



At the extreme northern limit of Polynesia lie the remote Hawai- 

 ian Islands, separated from the nearest land of any extent, by over 

 2,000 miles. In spite of their great distance from the islands to the 

 south, the general character of the flora is much the same, and 

 Malayan types are dominant as they are throughout Polynesia. 

 Nevertheless it is evident that the islands have been isolated for 

 a very long time, and in consequence the great majority of the 

 species, and a good many genera, are restricted to the Hawaiian 

 Archipelago. Hardly any part of the world has so large a propor- 

 tion of endemic species, upwards of 75% of the ferns and flowering 

 plants being unknown outside these islands. 



North America is the nearest continental land to Hawaii, being a 

 little more than 2,000 miles distant; but the floras of the two have 

 very little in common, in spite of the fact that the usually accepted 

 agents in distribution, viz., ocean currents, winds and migratory 

 birds, are all active between western America and Hawaii. 



That the Hawaiian islands have been isolated for a very long 

 period is amply proven by the peculiarities of both the animal and 

 plant inhabitants whose nearest relatives, however, are for the 

 most part found in the Malaysian and Australasian regions, and 

 not in America. 1 



The Hawaiian Archipelago consists of several large islands, with 

 a total area of nearly 6,500 square miles, lying between 18° 22' 

 and 21° 15' north latitude. From the main group a long series of 

 reefs and small islets extends for about eighteen degrees to the 



northwest. 



There is ample evidence that the large islands were formerly 

 united into a single land-mass which through gradual subsidence 

 has become separated into the islands as they now exist. The 

 northernmost island, Kauai, was the first to be cut off, as is indi- 

 cated by the broad and deep channel between it and its neigh- 

 bor to the south, Oahu. The long period of isolation of Kauai 

 is also indicated by the greater degree of endemism in the flora. 



The topography of the islands, especially the older ones, is 

 excessively rugged. The prevailing northeast trades bring torren- 



1 Campbell, D. H., The Derivation of the Flora of Hawaii, Leland Stanford Junior 

 Publications, 1919. 



