434 A NATURALIST IN THE PACIFIC chap. 



important part in plant distribution in temperate and arctic 

 latitudes. Ekstam strikes the true note for these regions when 

 discounting the agency of currents in the instance of the Spitz- 

 bergen flora, he regards the wind as the greatest factor in seed- 

 dispersal and after that the bird. The several interesting points 

 raised by this botanist are discussed in Chapter XXXIII. 



The Beach-Drift of Tropical Latitudes. 



Tropical beaches, as a rule, present a much greater abundance 

 and variety of stranded seeds and fruits than we find on beaches in 

 temperate latitudes. Observers in different parts of the tropics 

 have alluded to the enormous amount of vegetable drift floating in 

 the sea off the coasts, particularly in the vicinity of estuaries. 

 Though much of it is brought down by rivers, a good proportion is 

 also derived from the luxuriant vegetation that lines the beaches. 

 Gaudichaud speaks of the immeasurable quantity of drift (trees, 

 branches, leaves, flowers, fruits, and seeds) floating amongst the 

 islands of the Molucca Sea ; and Hemsley, who quotes this author, 

 gives other facts illustrating the same point. Moseley tells us that 

 seventy miles off the coast of New Guinea, H.M.S. Challenger 

 found the sea in places blocked with drift {^Bot. Chall. Exped. iv. 

 279, 284). When the author of this book was in the Solomon 

 Group, long lines of vegetable drift were frequently observed 

 floating among the islands. The Rewa River in Fiji carries down 

 a great amount of drift to the sea ; and as described in Chapter 

 XXXII, the Guayaquil River in Ecuador bears seaward an 

 enormous quantity of these materials. 



When we come upon this floating drift out at sea off an estuary, 

 we find, as Mr. Moseley pointed out, that the leaves have gone to 

 the bottom, whilst the floating islets, composed of the matted 

 vegetation lifted up from the shallows of a river channel, which 

 form such a feature in the Guayaquil River, have been dispersed or 

 sent to the bottom. However, a very large proportion of the seed- 

 drift brought down by a river from the interior has no effective 

 value for the purposes of dispersal. Many of the fruits and seeds 

 brought down from inland owe their presence in river-drift 

 entirely to the buoyancy acquired by the decay of the seeds. It is 

 in its lower course when it traverses the mangrove belt that a river 

 picks up most of the material that is of service in distributing the 

 species ; and this is mingled out at sea with the numerous buoyant 



