(b) Those possessing widely-ranging species besides, often, species confined to the Tahitian region, such as Grewia, Nelitris, Melastoma, Randia Geniostoma, Tabernæmontana, Fagræa, Bischoffia, Macaranga, and Ficus. The widely-ranging species is in many genera polymorphous.
(4) The absentees from Tahiti. Amongst the orders are the Meliaceæ, the Rhizophoreæ, and the Coniferæ. Amongst the genera, usually those with “stones” or large seeds an inch in size, such as Canarium, Dracontomelon, Myristica, Sterculia, Veitchia, &c. Numerous other absent genera might be named.
Fiji.—The Fijian genera not found either in Tahiti or Hawaii. These genera compose about half the Fijian flora, being at least 160 in number. Those especially discussed here are the following:—Hibbertia, Cananga, Sterculia, Trichospermum, Micromelum, Canarium, Dracontomelon, Begonia, Geissois, Dolicholobium, Lindenia, Myrmecodia, Hydnophytum, Couthovia, Limnanthemum, Myristica, Elatostema, Ceratophyllum, Gnetum, Veitchia, Rhaphidophora, Lemna, Wolffia, Scirpodendron. The Coniferæ are dealt with in [Chapter XXIV.]
Note appended on Marsilea
Having completed our discussion of the general dispersal of tropical genera, chiefly Indo-Malayan, over the Pacific islands, we pass on now to consider the more restricted distribution of non-endemic genera over this region. Here as before we take Hawaii, Tahiti, and Fiji as the three centres of distribution; and here also we deal with the flowering plants after excluding the orchids, the sedges, the grasses, the mountain-plants, and all plants introduced either by the aborigines or by white men.
Hawaii.
After excluding the endemic genera as well as those that are confined to the mountains, we find that this group possesses very few genera that do not occur in the Fijian and Tahitian regions, and fewer still that it owns in common with Tahiti to the exclusion of Fiji. On the other hand, we observe that Fiji possesses a great number of genera, mostly Asiatic in origin, that have not reached Hawaii, and in several cases are not known, from the Tahitian region. These contrasts might have been expected, since the Pacific islands have in later ages been mainly stocked from the Asiatic side of the Pacific, the principal route lying through the Fijian region.
As far as the flora of the lower levels (below 4,000 feet) is concerned, Hawaii only possesses a portion of that which Fiji has derived from the Old World, chiefly through Malaya. Although, as will be shown below, there is a noticeable contribution from America, it is very far from counterbalancing the loss which the Hawaiian flora has sustained in comparison with Fiji through the isolated position of the group. The want of variety, however, in the flora of the Hawaiian lower levels, which up to 4,000 or 5,000 feet represent the islands of the less elevated Fijian region, is in a small degree compensated for by the development of new genera and new species and by the great number of individuals. Trees like Metrosideros polymorpha and Aleurites moluccana, that in the southern groups form only one of many contributors to the forests, rise suddenly into prominence in the northern archipelago and form entire forests. Pandanus odoratissimus largely composes extensive forests in the province of Puna in the large island of Hawaii, extending several miles inland and nearly 2,000 feet up the mountain slopes.
The remarkable contrast between the Fijian flora, which is almost entirely tropical, and the Hawaiian flora, which on account of the great elevation of the islands is temperate as well as tropical, is brought into yet greater prominence when we look at it more closely and treat it numerically. The Hawaiian Group, it must be first observed, though possessing the same area as Fiji and presenting a far greater variety of climatic conditions, has only two-thirds the number of genera of flowering plants (see [Chapter XXI.], Table B). Whilst at least 200 of the Fijian genera of indigenous plants (excluding the orchids and the grasses) are not found in Hawaii, only about 100 of the Hawaiian genera are absent from Fiji, and the two groups possess about 100 genera in common. When we look more closely at the hundred Hawaiian genera not found in Fiji, we find that about sixty represent endemic genera (thirty-seven) and non-endemic mountain-genera (twenty-two), which naturally are not to be found in Fiji, so that there remain but a small number of genera distinguishing the tropical flora of Hawaii from the Fijian flora. When we take from them a few that occur in the Tahitian region, there is left a very small residuum characteristic of Hawaii alone to the exclusion of the Fijian and Tahitian regions of the South Pacific.