DERIVATION OF THE FLORA OF HAWAII 15 



brand is the endemic Marsilia villosa, which is apparently most nearly 

 related to the Western American M. vestita. 



The widespread Psilotum triquetrum and P. complanatum are com- 

 mon. 



Of ten species of Lycopodium, six are endemic, two (L. phlegmaria 

 and L. cernuum) are widespread tropical species, while two (L. volubile 

 and L. serratum) belong to Australasia and the Malayan region. 



There are three enedemic species of Selaginella and two others 

 which also occur in Southern Polynesia. 



SPERMATOPHYTES 



The flowering plants of Hawaii show an extraordinary degree of 

 endemism. According to Hillebrand, 14 out of 584 species of Dicotyledons 

 recognized as truly indigenous, no less than 500 are endemic. Of Mono- 

 cotyledons 74 out of 121 indigenous species are endemic. This gives a 

 percentage of 81.42 for all the spermatophytes and 85.62 for the Dico- 

 tyledons. There are many peculiar genera as well as species. 



Undoubtedly the aboriginal immigrants brought with them a con- 

 siderable number of plants, some of which have become naturalized. The 

 staple food plant, taro (Colocasia), the bread fruit, banana and cocoa- 

 nut doubtless reached the islands through human agency, and it is quite 

 likely that the Kukui (Aleurites) and Ohia (Eugenia), which now form 

 forests all over the islands, may have been introduced, as they are impor- 

 tant economic plants found throughout Southern Polynesia. 



The botanist is at once struck by the preponderance of Old World 

 genera among the trees and shrubs of the Hawaiian forest. Aside from 

 the Kukui and Ohia of the lower forest species which are doubtfully 

 indigenous most of the native trees and shrubs, which do not belong to 

 endemic genera, are members of extra-American genera occurring in 

 Australasia or the East Indian region. The commonest tree of the mid- 

 dle forest region is Metrosideros polymorpha, a species common in New 

 Zealand and throughout Polynesia. Perhaps next in abundance is the 

 Koa (Acacia koa), an acacia of the phyllode-bearing type, most species of 

 which belong to Australia. The screw-pine (Pandanus) and the related 

 creeper, Freycinetia, are members of the exclusively Old World family 

 Pandanaceae. The only genus of palms, Pritchardia, is confined to Poly- 

 nesia. Other familiar Old World genera are Pittosporum, Gardenia, 

 Santalum and Dracaena. Most of the species are endemic, and there are 

 a good many endemic genera. 



Some of the latter are remarkably developed and contain numerous 

 species. Perhaps the best known of these are several peculiar genera of 



14 Loc. cit., Introduction, p. xvii. 



