(2) The meagreness of the littoral flora is intensified by the tendency of some of the plants to extend inland and to desert the coasts, and by the occurrence on the beaches of peculiar species not found outside the Hawaiian Islands.
(3) The absence of the mangrove formation and of so many of the typical beach trees of the Pacific cannot be attributed either to the lack of suitable stations, or to climatic conditions, or to deficient floating power of the seed or fruit.
(4) As in the case of Tahiti, the mangroves and their associated plants are lacking because the floating seedlings of Rhizophora and Bruguiera, the pioneer plants of a mangrove-swamp, have failed to reach Hawaii in a fit condition for establishing themselves. The numerous plants that accompany a mangrove-swamp have thus been unable to find a home, though the buoyant powers of their fruits or seeds are often great.
(5) With the missing beach-trees, however, which possess fruits that can float for years unharmed in sea-water, no such incapacity is suggested. Most of them have large fruits, which could only reach Hawaii through the currents. This absence from the Hawaiian indigenous strand-plants of most, if not all, of the large-fruited species, where on account of size the agency of birds is absolutely excluded, is very remarkable; and it at first seems to throw grave suspicion on the efficacy of the currents for the whole strand-flora.
(6) It is, however, to be noticed that these large-fruited beach trees have not only failed to reach Hawaii but have also failed to reach America. The question thus acquires quite a different aspect, and America becomes the possible source of most of the Hawaiian plants with buoyant seeds or fruits.
(7) This subject is discussed in the next chapter; but it is here shown that at their best the currents have taken but a secondary part in stocking the Hawaiian beaches with their plants, since many of the plants have non-buoyant seeds or fruits.
(8) The drift stranded on the shores of the Hawaiian Islands is composed of logs from the north-west coast of North America. No drift from the south has been discovered; but it is not unlikely that future investigators will find some seed-drift from tropical America.
THE WORLD
SHOWING
OCEAN CURRENTS
John Bartholomew & Co., Edinr.