196 PLANTS, SEEDS, AND CURRENTS 



seed would just bring these fruits within the scope of the agency 

 of the Main Equatorial Current as a carrier of drift from West Africa 

 to Brazil. Though the greater number would probably not survive 

 this test, the few that did so would find on the first sandy coast 

 congenial conditions for establishing the plant. Its spread over the 

 West Indian region through the influence of the same swift current 

 would naturally follow. But before considering the possibility 

 that the New World has derived this species from West Africa, a 

 few remarks may be made on the distribution of the genus. 



There can be no doubt that the genus is preponderantly American, 

 whatever view we may take of the limitations of the species. Of the nine 

 species given in the Index Kewensis, five are peculiar to the New World, 

 three to the Old World (mainly Africa), and one is common to both 

 worlds. By some the species are regarded as fewer, but the American 

 preponderance remains. There is thus a basis of support for De Can- 

 dolle's original contention (Geogr. Bot., pp. 784, 792) that the species 

 common to both worlds, Chrysobalanus icaco, is American in origin. 

 On the other hand, this plant was regarded by J. D. Hooker and 

 Bentham as " possibly introduced " into America from Africa 

 (W. J. Hooker's Niger Flora, p. 336). We are thus on the horns 

 of a dilemma. If De Candolle is right, and certainly the ancient 

 story of the plant in the Florida Everglades gives support to his 

 view, it could not have been a gift from America to the Old World 

 under the present arrangement of the Atlantic currents. If Hooker 

 and Bentham are right, we can appeal to the currents, but we have 

 to face the facts that the genus is predominantly American and that 

 the plant in dispute has been for ages a denizen of the Everglades. 

 Then we have the singular feature, which Chrysobalanus holds in 

 common with several tropical genera existing in both worlds, a 

 feature indicated in the fact that the only species linking the western 

 and eastern hemispheres together are littoral plants that could 

 only cross the Atlantic by the agency of the currents in its narrowest 

 portion between Africa and Brazil, the implication being that Africa 

 would here figure as the giver and not as the recipient. The easiest 

 way out of this disconcerting situation may be to adopt the view that 

 we are not primarily concerned with means of dispersal, and that 

 the original centre of dispersion of the genus lay in the north. In 

 other words, the hypothesis advocated by Dyer may remove most 

 of our difficulties. 



