VIII LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 71 



Hawaii. We do not find amongst the truly indigenous coast flora 

 of this group any of the following trees : Barringtonia speciosa, 

 Calophyllum Inophyllum, Cerbera Odollam, Guettarda speciosa, 

 Hernandia peltata, Ochrosia parviflora, Pongamia glabra, Termi- 

 nalia Katappa, Terminalia littoralis, &c. It was also noted that 

 the currents had not only failed to establish these plants in Hawaii, 

 but that they had also failed to establish them in America, the 

 suggestion being that the Hawaiian Islands had been, in part at 

 least, stocked by the currents from America. That the Indo-Malayan 

 strand-plants in their extension eastward over the Pacific should 

 have failed to reach America, is a result we might have expected 

 from the arrangement of the currents. Yet mingled with them 

 we have plants like Ipomea pes caprae, Canavalia obtusifolia, and 

 Sophora tomentosa, that also occur in America. Since, however, 

 their seeds are not better adapted for accomplishing the passage 

 across the Pacific from the Old World to America than the equally 

 buoyant fruits of the above-named littoral trees that have failed, 

 the presumption arises that their home is in America, and that they 

 have performed the easier passage across the Pacific westward from 

 America to the Old World. 



The exclusion of so many characteristic shore- trees from America 

 that range often over the whole tropical region from the African 

 East Coast to the islands of the Central Pacific, is not a matter of 

 seed or fruit-buoyancy, but a matter concerned with the home of the 

 species, and with the arrangement of the currents. Those shore- 

 plants of this region that occur also in America have their home 

 in that continent, and have subsequently been carried across the 

 Pacific by the currents westward to the Asiatic shores. 



The only exceptions, that I can recall, to the rule that America 

 does not receive shore-plants dispersed by the currents from the 

 Old World, are presented by the three Australian genera, 

 Dodonaea, Scaevola, and Cassytha, of which widely spread littoral 

 species occur in America, namely, Scsevola Lobelia, Dodonaea 

 viscosa, and Cassytha filiformis. They offer, however, but little 

 difficulty, since, as pointed out in other parts of this work, 

 Dodonaea viscosa has probably been in part dispersed by man, 

 whilst the other two species are as well fitted for dispersal by birds 

 as by currents. The occurrence therefore of these species in 

 America does not necessarily raise the question of the currents. 



The same exclusive principle is illustrated in the scanty littoral 

 flora of Hawaii. Deprived, like America, of the characteristic 

 large-fruited beach-trees of the South Pacific, species that could 



