DISPERSAL OF PLANTS BY OCEAN CURRENTS. 73 



occurrence in the drift, it is interesting to note that on the eastern, 

 or weather, side of the island, where they are washed up, there is not 

 a single coconut grove near the water's edge, while on the western, or 

 lee, side, where groves have been planted, they grow so near the sea 

 that their roots are often bared by the waves. It seems probable that 

 coconuts grow in Guam only where they have been planted, except 

 in cases where nuts which have fallen from trees of established groves 

 have taken root. 



The seeds which occur in the drift owe their buoyancy to various 

 causes. Many of the "sea beans" inclose an air space between their 

 cotyledons; others have kernels which do not fill the ston}', water-tight 

 shells, but leave a space for air to keep them afloat; others have a 

 separate air chamber; others have fibrous envelopes or husks com- 

 posed of light tissue, and still others have woody or cork-like shells of 

 low specific gravit}'. 



Sea BEANS ADAPTED FOE FLOATING. — Among the hard stony seeds 

 of leguminous plants cast up on the shores of Guam are gray " nicker- 

 nuts" {Guilandina crista)^ called " pakao " by the Guam natives; 

 brown "horse-eye sea beans" {StisoloMum giganteum)^ with a con- 

 spicuous black raphe encircling nearly three-quarters of the periphery 

 of the seed, and the large flat "snuffbox beans" {Leiix jiJuiseoloides), 

 called "bayog" or "badyog" in Guam and "cacoons" in the West 

 Indies. These "sea beans," or their closely allied representatives 

 growing in the West Indies, were figured as early as 1693 in an 

 account of the objects cast up by the sea on the Orkney Islands by 

 James Wallace, who knew nothing of their origin." They were 

 recognized at once by Hans Sloane as the seeds of plants he had 

 seen growing in Jamaica and which he had included in his catalogue 

 of Jamaica plants. Their occurrence "on the shores where they were 

 collected, so far removed from the place of their origin, suggested 

 to Sloane the existence of the current which was afterwards known 

 as the Gulf Stream. Sloane published a paper on the subject in the 

 Philosophical Transactions of Ijondon in 1696, in which he for the 

 first time offered to the world the true explanation of the means by 

 which they were transported.* 



« ' ' Cast up on the Shoar there are very oft those pretty Nutts, of which they use to 

 make Snuff-boxes. There are four sorts of them, the figures of which are set down. ' ' 

 Description Orkney Islands, p. 14, 1693. 



6 " How these several Beans should come to the Scotch Isles, and one of them to 

 Ireland, seems very hard to determine. It is easy to conceive, that growing in 

 Jamaica in the Woods, they may either fall from the Trees into the Elvers or be any 

 other way conveyed by them into the Sea: it is likewise easie to believe, that being 

 got to Sea, and floating in it in the neighbourhood of that island, they may be car- 

 ried from thence by the Wind and Current, which meeting witli a stop on the main 

 continent of Am. is forced through the Oulph of Florida, or Canal of Bahama, going 

 there constantly E. and into the N. American Sea; for the .... Sargasso grows on 



