22 A NATURALIST IN THE PACIFIC CH. n 



treated. Enough, however, has been said to illustrate the character 

 of the sorting-process by which in the course of ages the plants 

 with buoyant seeds or seedvessels have been gathered at the coast. 

 This is indicated : 



(1) By the far greater proportion of species with buoyant seeds 

 and seedvessels amongst the shore plants than among the inland 

 plants. 



(2) By the circumstance that almost all the seeds or fruits that 

 float unharmed for long periods belong to shore plants. 



(3) By the fact that when a genus has both inland and littoral 

 species, the seeds or fruits of the coast species as a rule float for a 

 long time, whilst those of the inland species either sink at once or 

 float only for a short period. 



These results, therefore, justify our dividing the flora of our 

 island into two groups, the one including the plants with buoyant 

 seeds or fruits and comprising most of the littoral plants, the 

 other including the plants with non-buoyant seeds or fruits, a 

 group which contains almost all the inland plants and indeed 

 nine-tenths of the flora. This classification is a very crude one ; 

 but it enables us at once to assign a value to the agency of 

 currents in stocking a Pacific island with its plants. Yet this is 

 but the initial step in an inquiry that branches off in a thousand 

 different ways, even if restricted to the littoral plants. There are 

 a host of difficulties connected with the history of the strand-flora 

 of such an island which can only be properly gauged when viewed 

 from various standpoints. 



