Looking at the indications of these four widely ranging plants, the Chilian strawberry (Fragaria chilensis), the Sun-dew (Drosera longifolia), Nertera depressa, and Luzula campestris, it may be inferred that with the exception of Nertera they all reached Hawaii from either the Asiatic or American sides of the North Pacific, the last route being evident in the case of the strawberry. Nertera depressa was probably derived from southern latitudes.
Summary.
(1) The second era of the flowering plants of the Pacific islands is indicated by the non-endemic genera. Here also the isolating influences have been generally active, and the work of dispersal is in some regions largely suspended. Thus in Hawaii nearly half the non-endemic genera possess only species that are restricted to the group, whilst in Fiji and Tahiti about a fourth are thus isolated.
(2) The contrast in the elevations of the islands of the Hawaiian, Tahitian, and Fijian regions is reflected in the development of an extensive mountain-flora in Hawaii, in its scanty development in Tahiti, and, excluding the Fijian conifers, in a mere remnant in Fiji and Samoa.
(3) The influence of isolation has been very active in the Hawaiian mountains, since about two-thirds of the genera contain only species confined to the group, and are thus disconnected from the world outside.
(4) Amongst these disconnected Hawaiian mountain genera, Antarctic or New Zealand genera, like Acæna, Gunnera, Coprosma, and Lagenophora, constitute nearly a third. The American element, represented, for instance, by Sanicula and Sisyrinchium, is small; whilst the genera found on both sides of the Pacific form more than one-half of the total, and include genera like Ranunculus, Viola, Rubus, Artemisia, Vaccinium, and Plantago, that often represent the flora of the temperate zone on the summits of tropical mountains. Three-fourths of these genera are not found either in Fiji or in Tahiti.
(5) The proportion of the disconnected Hawaiian mountain genera possessing seeds or seedvessels suited for dispersal in a bird’s plumage is very large, quite half belonging to this category; whilst only about a fourth have fruits that would be dispersed by frugivorous birds.
(6) The Hawaiian mountain genera that still remain in touch with the external world through species found outside the islands whilst other species are confined to the group, present a later stage in the plant-stocking. Their widely ranging species, which would be dispersed either by frugivorous birds, as with Santalum and Cyathodes, or in birds’ plumage, as with Lysimachia, Carex, and Deyeuxia, seem to indicate that the main lines of migration for these genera have been from temperate Asia and from the Australian and New Zealand region, the last by way of Eastern Polynesia.
(7) The latest stage of the Hawaiian mountain-flora is exemplified by those genera that are only represented in the group by a solitary widely-ranging species, such as Fragaria chilensis, Nertera depressa, Drosera longifolia, and Luzula campestris. It is our own age; and birds are shown to be actual agents in the dispersal of the two first-named species and to be probable agents with the two other species. The two last-named species probably reached Hawaii from one or other side of the North Pacific; whilst Fragaria chilensis doubtless hails from the adjacent part of the American continent, and Nertera depressa from high southern latitudes by way of Tahiti.