VIII LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 75 



(/) A small number of the strand-plants of the Pacific islands 

 that are dispersed by currents occur in America as well as in the 

 Old World ; and questions of prime importance arise when we 

 have to decide whether their home is in the Old World or in the 

 New World. 



(g) Good reasons are given for regarding them as chiefly of 

 American origin ; and it is shown that America with regard to 

 the arrangement of the currents stands in the singular relation of 

 being a disperser but not a recipient of shore-plants. 



(k) It is pointed out that the tropical shore-plants that are dis- 

 tributed by currents belong to two great regions which are the 

 effect of the present arrangement of the currents, viz., the American 

 including the West Coast of Africa, and the Asiatic comprising the 

 remainder of the tropical zone. Each region has its own plants, 

 and those that occur in both, being in fact distributed all round the 

 tropics, are regarded, according to the principle above stated, as 

 having their home in the American region. 



(z) The occurrence of the same strand species on the Pacific and 

 Atlantic coasts of tropical America is regarded as indicating that 

 the arrangement of the existing species of its shore-plants, more 

 particularly of the mangroves, antedates the emergence of the 

 Panama Isthmus. This hypothesis is not needed for the coast 

 plants like Entada scandens that occur inland, since we can now 

 observe their seeds being carried down into the Atlantic and 

 Pacific Oceans by rivers draining the opposite slopes of the same 

 " divide " in the Panama Isthmus. 



(j) It is shov/n that the currents of the Pacific have failed to 

 establish the numerous beach-trees (possessing buoyant fruits) of 

 the Pacific islands, not only in the Hawaiian Group, but also on 

 the coast of America ; and it is therefore argued that we should 

 expect the Hawaiian Group to have received through the currents 

 its shore-plants with buoyant seeds or fruits from the tropical west 

 coasts of America. 



(k) In support of this contention it is pointed out that most of 

 the Hawaiian strand-plants that are dispersed by the currents are 

 found in America, and some indeed in America to the exclusion 

 of the Old World. 



(/) The arrangement of the currents in the North Pacific also 

 favours the view that the Hawaiian Islands are more likely to 

 receive plants by the agency of the currents from America than 

 from the Asiatic side of the Pacific. 



