(3) It also wants many of the plants that grow in the vicinity of such swamps.
(4) But since the plants last-mentioned often possess fruits or seeds capable of being carried great distances by the currents, their absence is to be attributed to the necessary conditions being lacking on account of the failure of the mangroves.
(5) Most of the beach plants, however, owe their existence in this region to the transport of their buoyant fruits or seeds by the currents.
(6) The negative features of the Tahitian strand-flora are mostly to be connected with the absence of Rhizophora and Bruguiera, the pioneers of the mangrove-swamp; and their absence is, in turn, to be attributed to the inability of their floating seedlings to reach this region in a fit condition for establishing themselves.
CHAPTER VII
THE HAWAIIAN STRAND-FLORA
Its poverty.—Its negative features.—Their explanation.—The subordinate part taken by the currents.—The Oregon drift.—The inland extension of the beach plants.—Summary.
Compared with the rich strand-flora of Fiji, that of Hawaii presents but a sorry aspect. In the number of species (30) it does not amount to half; whilst it lacks the great mangrove-formation and the luxuriant vegetation accompanying it that gives so much character to the shores and estuaries of Fiji. Strangely enough, it is also deprived of most of the familiar trees that, whether in foliage, in flower, or in fruit, form the chief attraction of the sandy beaches of the Pacific islands.
Neither the mangroves, therefore, nor the plants of the intermediate formation, are to be found in Hawaii; and when we reflect that the absentees from the beach formation include most of the trees, under the shade of which the visitor to the Pacific islands can nearly always find protection from the fierce rays of a tropical sun, it cannot be a matter of surprise that this littoral flora has such a poverty-stricken appearance. We look in vain for such shady beach trees as Barringtonia speciosa, Terminalia Katappa, and Hernandia peltata; and we are lucky if we find some small trees under which we can obtain a scanty shade.
I have been speaking, of course, of the indigenous shore-plants, those that have arrived at these islands without the assistance of man. Yet it must be added that the existing littoral flora does include some of the missing indigenous trees, though rarely in any number. There is, however, scarcely one of them that is regarded by Dr. Hillebrand as having formed part of the original flora. That botanist would indeed rob the present beach flora, scanty as it is, of most of its conspicuous plants, as far as their claims to be considered indigenous are concerned. Dr. Hillebrand indeed includes Calophyllum Inophyllum, Hibiscus tiliaceus, Thespesia populnea, Morinda citrifolia, Cordia subcordata, and Pandanus odoratissimus in the present Hawaiian flora, and nearly all of them are to be found at times at the coast as well as inland; but he regards all, excepting the last-named, as having been introduced by the aborigines. I was not inclined at first to go quite so far as Dr. Hillebrand in this direction; but he carefully considered the case of each individual plant, and, remembering his sojourn of twenty years in the islands, his authority cannot be lightly put aside. In the list of Hawaiian strand-plants given in [Note 28] there are several species not always littoral in the group, but typically littoral in other tropical regions. One species, Ipomœa glaberrima, Boj., has not been recorded before from these islands.
A strong reason in favour of the contention of this botanist is that all the trees above-named are useful in some way to the natives; and, indeed, when we look at the works dealing with the floras of the islands of the South Pacific, we observe that in almost all the groups one or other of these six trees bears the reputation of having been introduced by the aborigines. All of them in their turn lose their fame as truly indigenous plants in some group or other. The occurrence of two or three useless South Pacific beach trees, that are known to be dispersed by the currents, in the indigenous strand-flora of Hawaii, would go far to invalidate Dr. Hillebrand’s argument, since the six trees in dispute are also known to be dispersed by the currents. But such trees are not to be found; and we look in vain for trees like Cerbera Odollam, Guettarda speciosa, Gyrocarpus Jacquini, and Hernandia peltata, that are spread far and wide over the beaches of the South Pacific.