DISTRIBUTION OF THE MOEE PROMINENT NATUEAL OEDEES. 275 



species having a very wide range ; but how much of that is due to human agency, and 

 how much to other agencies, such as oceanic currents, is not easy to determine. Of 

 the American genera of palms only two, excluding Cocos, are represented elsewhere ; 

 these are Elms and Baphia, both otherwise only African. Drude*, however, treats 

 BapMa vinifera as an African type, introduced by some means in America, though 

 ranging on the sea-shore from the mouth of the Amazon to Nicaragua ; and he further 

 suggests that the African Elms, though specifically distinct from the American, is, in 

 like manner, of American origin, of very remote introduction in Africa, may be 

 " thousands of years." He bases his argument on the fact that all the Cocoinese, with 

 this exception, and the now widely-spread Cocos nucifera, are exclusively American f. 

 Of course, admitting an unlimited period to elapse since migration or conveyance took 

 place, the origin of many outliers might be explained in this way. But to return to 

 palms generally ; it is not only species and genera that are comparatively restricted in 

 their range ; the same law applies more largely to the tribes than is the case in most 

 large orders. Drude J shows that of ten natural tribes of palms only three are common 

 to America and the Old World, and only two of them belt the world. 



Palms are spread over about half the surface of the land, and are essentially plants 

 of the tropical zone, where they are generally spread, rapidly thinning-out both in 

 species and individuals outside of the tropics. At present about 1100 species of palm 

 are known, and these have been divided into 140 genera — numbers low in relation to the 

 prominent and proportional position they occupy in tropical scenery. Nearly a score of 

 orders are more numerous in species, but not one forms so large a part of the vegetation. 

 Some palms grow intermixed with other trees, whilst others grow in groves of countless 

 individuals; and they certainly constitute the most striking feature in tropical vege- 

 tation. America is, perhaps, the richest country in palms, which culminate in numbers 

 in the Amazon region; but they are also very numerous in the Malay Archipelago. 

 The highest latitudinal limits of palms in the Old World are about 44° in New 

 Zealand (where there is one species), 35° in Japan, and 43° in Europe; in each case 

 represented by solitary outliers. In South America one endemic species inhabits Chili 

 up to about 38° latitude, and one Juan Fernandez in 34°. In western North America 

 the limit is about 34°, and in eastern about 36°. Nearly all these outlying palms belong 

 to monotypic genera peculiar to each region. 



The enumeration of Mexican and Central-American palms (iii. pp. 400-415) contains 

 118 species, belonging to twenty-four genera; but so little is known of the palms of 

 the purely tropical parts that further investigations may considerably augment these 



* " Geographische Verbreitung der Palmen," Petermann's Mittheilungen, 1878, p. 103. 



f MapMa vinifera, Beauv., var. tcedigera, syn. B. nicaraguensis, (Erst., was accidentally omitted from our dis- 

 tribution table, and Cocos nucifera was intentionally excluded, like many other cultivated plants. Nevertheless, 

 the latter is almost certainly indigenous in America (and most likely in Central America), to which country all 

 the other species of Cocos are peculiar. . % Botanische Zeitung, 1876, p. 801. 



biol. cente.-amek., Bot. Vol. IV., August 1887. 2o 



