It is evident that in one or two cases the connection between the representatives of the “Antarctic” genera on the Hawaiian uplands and those of high southern latitudes has only been recently broken off. Thus with reference to the Hawaiian species of the Cyperaceous genus, Uncinia, it may be observed that although Hillebrand regards it as a distinct species, Hemsley (Intr. Bot. Chall. Exped., p. 31) remarks that it is very near if not the same as a New Zealand species, an affinity very significant of the source of the mountain plants of this group that are derived from these southern latitudes.
The next component to be recognised in these Hawaiian mountain genera with peculiar species is a small special American element; and in this connection Sanicula and Sisyrinchium may be especially mentioned. The first is mainly North American, and particularly Californian; but there are two solitary species found on the continents and in oceanic islands such as the Azores. The continental species, Sanicula europæa, occurs not only in Europe and Central Asia, but in South Africa, and at high elevations on the mountains of Equatorial Africa and of Madagascar. It is not, however, with this widely ranging species that Sanicula sandwicensis is related, but with S. menziesii, a species from California and Oregon (Hillebrand). Sisyrinchium is confined to temperate and tropical America; but a singular and suggestive outlier of the genus (S. bermudiana) is found in Bermuda.
The mountain genera that are distributed on both sides of the Pacific constitute about three-fifths of the total. So far as my scanty data show, they seem to have reached Hawaii from the four quarters of the compass. The probable southerly origin of Plantago has been already indicated. Hillebrand notes the great resemblance between Lobelia gaudichaudii and an undescribed species from the Liukiu Islands, lying on the west side of the Pacific. It is likely, also, that the genus Ranunculus reached Hawaii from the west, since one of the species, R. mauiensis, resembles R. repens of the Old World (Hillebrand); whilst the other, R. hawaiiensis, comes near R. sericeus of Mauritius (Drake del Castillo). On the other hand, the genus Rubus may hail from an American source, since, in the opinion of Gray, Rubus hawaiiensis, one of the mountain raspberries, finds its nearest relative in R. spectabilis from the north-west coast of America; and there are reasons for believing, as will subsequently be shown, that the genus Artemisia has an American source. It is also probable that some of these genera have reached Hawaii from the north, since it is likely, as pointed out in a later page, that the Carices of the Hawaiian uplands came originally from north-eastern Asia.
In the previous paragraphs the mountain genera have been considered with especial reference to their distribution and source beyond the confines of the Pacific. If we now briefly discuss them from the standpoint of their distribution within the Pacific, or rather as concerning their presence or absence in the Fijian and Tahitian groups, we shall see that to a large extent Hawaii has received its mountain genera of this era independently of the other Pacific groups.
| Mountain genera possessing only peculiar species, in Hawaii only | 20 |
| Mountain genera possessing only peculiar species, in Hawaii and Fiji | 2 |
| Mountain genera possessing only peculiar species, in Hawaii and Tahiti | 0 |
| Mountain genera possessing only peculiar species, in all three groups | 4 |
| — | |
| 26 |
It is here shown that three-fourths of the genera of the Hawaiian mountains in this era are not found either in Fiji or Tahiti. This, as before pointed out, is mainly to be attributed to the greater elevation of the Hawaiian Islands. Had there been an island 13,000 to 14,000 feet in height in Fiji, we cannot think that any such contrast in the floras would have existed. The temperate genera of the Hawaiian uplands would have been largely represented in the Fijian flora. Yet although we do not find such genera as Ranunculus, Geranium, Sanicula, Uncinia, &c., in Fiji and Tahiti, a small number of the Hawaiian mountain genera have obtained a scanty footing. This is what we might have expected. Thus, Lagenophora has been found on the mountains of Vanua Levu, and Vaccinium in Tahiti and Rarotonga; whilst Coprosma and Astelia occur on the tops of some of the mountains in both regions. In Fiji their distribution seems sporadic, as shown not in Lagenophora alone, but also by Astelia, which has been found only on the summit of Kandavu.
The Capacities for Dispersal of the Hawaiian Non-endemic Mountain Genera possessing only Peculiar Species.—As shown in the Table, seven, or 27 per cent., of these genera have fleshy fruits that would attract frugivorous birds. In three cases (Gunnera, Coprosma, Myoporum) they are drupes, in three others (Rubus, Vaccinium, Astelia) they are berries, and in one (Exocarpus) there is a nut with a fleshy perigone. It is particularly interesting to notice that frugivorous birds, and I include here granivorous birds that are known to be frugivorous at times, could have transported seeds of the “Antarctic” flora to this group. We can observe the process in operation in our own time within the limits of the group. It has been long known, and we find it referred to in the pages of Hillebrand’s work, that the wild mountain-goose (Bernicla sandwicensis) feeds upon the fruits of Coprosma ernodeoides, and of Vaccinium reticulatum, the famous “ohelo.” The fruits of the first are known to the natives as “kukai neenee” (droppings of geese), and the hard stones or pyrenes are very well suited for withstanding the risks of the digestive process. I found a number of these pyrenes in the stomach of a mountain-goose shot by my companion, Dr. Krämer, high up the slopes of Mauna Loa.
According to Mr. Perkins, Chloridops kona, a big Hawaiian finch, feeds on the fruits of the bastard sandal-tree (Myoporum sandwicense). There are no “impossible fruits” among the mountain genera of Hawaii, that is to say, fruits so large that bird agency must be excluded. All of them are practicable in point of size. Thus amongst the largest, the “stones” of Gunnera would not exceed 1⁄5 of an inch (5 mm.), and those of Myoporum scarcely 1⁄4 of an inch (6 mm.); whilst the nuts of Exocarpus range in the Hawaiian species from 3⁄10 to 6⁄10 of an inch (7-15 mm.), and the beans of Sophora chrysophylla do not at the most exceed 1⁄4 of an inch (6 mm.).
The principal feature, however, which these mountain genera exhibit from the point of view of their dispersal is the number of plants possessing seeds or fruits capable of adhering to plumage. Half of these genera are thus characterised. Of these Sanicula and Acæna represent the ordinary hooked fruits; whilst the fruits of the Grasses and Sedges, Agrostis, Deschampsia, Trisetum, Poa, Oreobolus, and Uncinia, are enabled by means of their awns or of their serrated beaks to attach themselves to plumage, and the same may be said of the carpels of Geranium. The fruits of Lagenophora and the seeds of Plantago display the capacity of adhesiveness by means of a gummy secretion.
One or two of these genera need further mention. I will first take Acæna, which is spread all over the south temperate zone both on the continents and on the islands. The Hawaiian species (A. exigua) forms tussocky growths on the swampy summits of Mount Eeka in Maui, and in Kauai, at an elevation of 6,000 feet above the sea. Numerous observers refer to the probable mode of dispersal of the genus in the “Antarctic” and neighbouring islands. Captain Carmichael, in the instance of Acæna sanguisorbæ on Tristan da Cunha, observes that it overruns the low ground. Its burr-like fruit, as he describes, “fixes itself on the slightest touch into one’s clothes, and falling into a hundred pieces covers one all over with an unseemly crust of prickly seeds not to be got rid of without infinite labour” (Trans. Linn. Soc., xii. 483, 1818). Both Mr. Moseley (Wallace’s Island Life, p. 250) and Dr. Kidder (Bull. U.S. Nat. Mus., 2) refer to the burrowing habits of the Petrels, Puffins, and other sea-birds amongst the vegetation covering the ground in Tristan da Cunha, Marion Island, Kerguelen, &c., in places where Acæna, amongst other plants, thrives. Mr. Moseley remarks that the fruits of this genus stick like burrs to feathers, and he looks to sea-birds for the dispersal of this and similar plants over the ocean. He especially notes that the Petrels and other seafowl burrow and breed high up the mountain-slopes of tropical islands as in Tahiti, Viti Levu, Hawaii, and Jamaica.... It should be noted in the case of the Hawaiian endemic species that it has been found only on two mountain tops; and that however active may be the dispersal of the genus in south temperate latitudes now, the Hawaiian Islands lie outside the present area of dispersal.