DISPERSAL OF PLANTS BY OCEAN CURRENTS. 73 



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

 or weather, side of the island, where they are washed u}), there is not 

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

 lee, side, where groves have been planted, the}- 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 till the stony, 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 w^oody or cork-like shells of 

 low specitic gravity. 



Sea beans adapted for floating. — Among the hard stony seeds 

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

 nuts'' {Gu'dandlna crista)^ called "pakao" by the Guam natives; 

 brown '•horse-e3"e sea beans'' {StlzoloHujii gHjanteum)^ with a con- 

 spicuous black raphe encircling nearl}' three-quarters of the periphery 

 of the seed, and the large fiat " snufibox beans'' {Latx plia^eoloidei^^ 

 called ''baj'og" or ''badyog" in Guam and "cacoons" in the West 

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

 srrowino- in the West Indies, were tigured as earlv as 1()1>3 in an 

 account of the objects cast up by the sea on the Orkney Islands l)y 

 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. Tiieir 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 pul)lished a paper on the subject in the 

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

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

 which the}' 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. 1-t, 1693. 



^" 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 Rivers or l)e 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 l)y the Wind and Current, which meeting with a stop on the main 

 continent of Am. is forced through the < inlph of Florida, or Canal of P>aliama, going 

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



