DERIVATION OF THE FLORA OF HAWAII 23 



lated to Andean types ; but in view of the wide distribution of the family, 

 this seems questionable. 



It is pretty safe to assume that the Hawaiian species of evident 

 North American affinities have reached the islands as immigrants subse- 

 quent to their isolation. As there are a number of migratory birds, such 

 as the golden plover, which regularly visit Hawaii, from Alaska, as well 

 as various species of waterfowl, it may be that these birds have played a 

 part in the introduction of some of these American elements of the flora 

 whose seeds or fruits are not adapted to wind carriage. Among the 

 genera which perhaps fall in this category are Rubus, Fragaria, Drosera, 

 Vaccinium, Sisyrynchium. Such aquatic plants as Ruppia and Potomo- 

 geton may very well have been introduced by ducks or other water birds. 



As to the Compositae of American affinities, as already stated, it 

 seems more likely that their fruits have been wind-borne than that they 

 were carried by birds. The prevailing northeast trade wind makes it 

 possible that this has been one of the agents by which North American 

 plants have reached Hawaii. It is hardly likely that the drift from the 

 northwest American coast which occasionally reaches Hawaii has played 

 any conspicuous role in plant introduction, as it is not likely that plants 

 from Alaska and British Columbia would find a very congenial habitat 

 on the shores of Hawaii. 



The objection has been brought against the continental theory of 

 the Hawaiian archipelago that certain types are absent, which on this 

 theory one would expect to find. First in importance are conifers like 

 Araucaria, Podocarpus and Agathis, characteristic genera of the South- 

 ern Pacific regions, like New Zealand, Australia and Malaysia. Another 

 notable case is the genus Ficus, practically universally distributed 

 through the tropics of both hemispheres. Another almost equally notable 

 instance is the large family Araceae represented by but two species, 

 both of them almost certainly introduced since the occupation of the 

 islands by man. There are a number of other cases which could be cited, 

 and these objections are real ones and not easy to explain. 



Perhaps the most probable explanation is the possibility of the ex- 

 tinction of these forms, after the isolation of the islands, which made it 

 impossible for them to be replaced. There are plenty of examples of 

 such disappearance of plants from regions which they once inhabited. 

 We have but to remember the many cases of Tertiary fossils, showing 

 the former wide range of many genera, now restricted in their distribu- 

 tion. Sequoia, Taxodium, Liriodendron may be cited out of a long list of 

 such genera, whose disappearance from many regions where they once 

 flourished is amply proven by the fossil record. 



Unfortunately there are no fossils in Hawaii to throw light upon the 



