DERIVATION OF THE FLORA OF HAWAII 



widespread Drosera longifolia, dwarf geraniums, violets, lobelias, vac- 

 ciniums, Selaginella, Schizaea and others. 



On the lofty mountains of Maui and Hawaii there is a forest zone 

 reaching up to 11,500 feet, but this is much less varied than the middle 

 forest. 



As might be expected from the extreme isolation of the islands, both 

 the flora and fauna are highly specialized, the proportion of endemic 

 species being very great. According to Hillebrand eighty per cent of the 

 vascular plants are peculiar to Hawaii, while no less than eighty-five per 

 cent of the Dicotyledons are confined to the islands. The fauna shows 

 very much the same high proportion of endemism. It is plain that 

 whether or not there have been land connections formerly, the islands 

 have been isolated for a very long period. 



Among the most characteristic animals are the land snails, which 

 have been collected assiduously and very thoroughly studied. As the result 

 of his studies on these molluscs, Pilsbry 7 came to the conclusion that 

 they must have reached the islands at a very remote period, through some 

 land connection, as they are quite unsuited to any conceivable form of 

 transportation over such distances as now separate Hawaii from the 

 mainland. They are inhabitants of the humid mountain forests, and ap- 

 parently cannot survive exposure to heat and dryness, such as would be 

 necessary in case they were transported from a distance by driftwood, 

 as has usually been assumed to have been their means of introduction 

 into the islands. 



According to Pilsbry, they are all very old types, there being a com- 

 plete absence of the more modern snails from the fauna. Their nearest 

 relatives belong in Southern Polynesia, and these in turn are more dis- 

 tantly related to forms of the adjacent Asiatic shores and have nothing 

 in common with American types. This indicates that the existing islands 

 once formed a single, much larger area, which was presumably connected 

 more or less directly to similar large areas in what is now Southern 

 Polynesia. 



The occurrence of certain plants identical with or closely related to 

 those of the Southern Pacific areas presents the same problem as the land 

 snails. There is a rich liverwort flora, including a number of species 

 whose presence is hard to explain, except on the theory that they are 

 remnants of an ancient continental flora. They are plants of great deli- 

 cacy, often confined to the higher altitudes of the rain forest, where 

 there is almost constant precipitation. Such species are incapable of sur- 



r Loc. cit. 



