The small seeds of the capsular fruits of Lysimachia could be transported in birds’ plumage or in dried soil attached to their feet or feathers. The seed-like fruits of Chenopodium were probably dispersed by some granivorous bird, much as nowadays our partridges carry about in their stomachs the similar fruits of Atriplex. The long-awned fruits of Deyeuxia were, it is likely, transported in birds’ plumage, and doubtless also those of Panicum; whilst the nutlets of Carex and Rhynchospora might have been carried about in a similar fashion.
The distribution of the non-endemic species of these Hawaiian mountain genera may perhaps aid us in determining the original source of the genus as well as in confirming the conclusions formed concerning the other mountain genera that only possess species restricted to the group. Lysimachia, Chenopodium, Carex, Rhynchospora, Deyeuxia, and Panicum are found in both the Old and New Worlds. Since Hillebrand remarks that one of the six species of Lysimachia (L. spathulata) occurs in Japan and in the Liukiu, Bonin, and Marianne groups, we have here a valuable indication of the route followed by a genus that has not been recorded from the oceanic groups of the South Pacific.
The capricious distribution of the genus Carex in the Pacific is remarkable, and it is noticed by Hemsley in the Introduction to the Botany of the “Challenger” Expedition. No species have been recorded from Tahiti, the Marquesas, and Rarotonga, but three Fijian species are mentioned by Hemsley, and there is another in Samoa. Of the five Hawaiian species given by Hillebrand, two are endemic. Of the rest, C. wahuensis (oahuensis), Meyer, occurs also in Korea and Japan, whilst C. brunnea, Thunb., is found in Japan and Australia, and the third, C. propinqua, Nees., occurs all round the border of the Pacific Ocean, from Kamschatka through Alaska south to the Straits of Magellan. These three species all possess a home in common in north-east Asia, and probably there lies the source of the Hawaiian species of Carex—a conclusion which would help to explain the irregular distribution of the genus amongst the South Pacific groups.
The genus Rhynchospora occurs alike in the Hawaiian, Tahitian, and Fijian islands; but the groups in the North and South Pacific seem to have been independently supplied with the original species, since R. aurea, a widely spread tropical species, ranging the South Pacific from New Caledonia to Tahiti, has not been recorded from Hawaii. A connection between Hawaii and the Australian region seems to be indicated by a species of Deyeuxia (D. forsteri) that is found also in Easter Island, Australia, and New Zealand, and by the presence of the Australian and New Zealand genus Cyathodes in Hawaii, though the existence of a species common to both Tahiti and Hawaii goes to show that the route followed by the genus lay through Eastern Polynesia. It is also not unlikely that the genus Santalum reached Hawaii through Eastern Polynesia, since two forms found in Hawaii and Tahiti are closely allied, and are, in fact, regarded by Drake del Castillo as the same species. The genus occurs in tropical Asia, Australia, and New Zealand.
Looking at the indications above given, I should be inclined to think that the genera Lysimachia and Carex reached the Hawaiian mountains from temperate Asia or the islands off its Pacific coast, and that Cyathodes, Santalum, and Deyeuxia hail from the Australian or New Zealand region by way of Eastern Polynesia.
The Mountain Genera possessing no Endemic Species.—The few remaining mountain plants of Hawaii to be considered are solitary, widely ranging species of genera that here possess no peculiar species. Such may be regarded as belonging to the latest age of the indigenous plants. They still keep up, or kept up until recently, the connection with the world outside Hawaii, and among them one may name here Fragaria chilensis, Drosera longifolia, Nertera depressa, and Luzula campestris.
Fragaria chilensis, the Chilian strawberry, flourishes at elevations of between 4,000 and 6,000 feet on the Hawaiian mountains. Its fruits, according to Hillebrand and other authors, are much appreciated by the wild goose of the islands. This plant ranges in America from Chile north to Alaska; and Drake del Castillo is doubtless on safe ground when he assumes that a congener of this bird originally brought the species from the nearest part of the American continent, namely from California (Remarques, &c., p. 8). In this connection it should be remembered that one of the endemic mountain-raspberries of Hawaii (Rubus hawaiiensis) finds its nearest relative, according to Gray, in Rubus spectabilis, a species from the north-west coast of America.
The species of Sun-dew, Drosera longifolia, hitherto found only on the marshy tableland of Kauai at an elevation of 4,000 feet above the sea, occurs both in Asia and North America. Its minute fusiform seeds are very light in weight, and might readily become entangled in a bird’s plumage, or they could be carried in adherent dried mud.
Luzula campestris, which grows on the high mountains of the Hawaiian group from 3,000 feet upward, is also found in Tahiti. It is widely distributed in cool latitudes, and there is no special indication of its source. Its seeds are especially well suited for adhering to birds’ feathers. When experimenting on these seeds in 1893 I ascertained that whether freshly gathered or kept for more than a year they became on wetting coated with mucus, and adhered firmly to a feather on drying. There are many ways in which the “sticky” seeds in wet weather might fasten themselves to a bird’s plumage. The plant-materials might be used, for instance, for making nests. The Sea Eagle (Aquila albicilla), as we learn from Mr. Napier (Lakes and Rivers), uses materials derived from Luzula sylvatica in the construction of its nest.
Nertera depressa, a creeping Rubiaceous plant, with red, fleshy drupes containing two coriaceous pyrenes, is found in all the Hawaiian Islands at elevations of 2,500 to 5,000 feet, and it grows on the mountains of Tahiti at altitudes over 3,000 feet. The genus is widely diffused over the southern hemisphere. This particular species is characteristic of the Antarctic flora, being found all round the south temperate zone (excepting South Africa) in New Zealand, Fuegia, the Falkland Islands, and Tristan da Cunha, and extending up the Andes to Mexico, occurring also on the summits of Malayan mountains at elevations of 9,000 to 10,500 feet above the sea, as on Pangerango in West Java (Schimper), and on Kinabalu in North Borneo (Stapf). Captain Carmichael, who resided on Tristan da Cunha in the early part of last century, states (Trans. Linn. Soc., xii. 483) that its drupes are eaten by a species of thrush and by a bunting. Professor Moseley, who visited the island in the Challenger many years after, remarks that its fruits are “the favourite food of the remarkable endemic thrush, Nesocichla eremita,” the bunting being Emberiza brasiliensis (Bot. Chall. Exped., ii. 141). It would seem most likely that the Hawaiian Islands received this representative of the Antarctic flora through the Tahitian Islands, as in the case of the species of Cyathodes common to both these groups.