272 ORIGIN AND DISTRIBUTION OF THE COCOA PALM. 



interest because it was intended to explain the probability that the 

 yam was not in use in Sanscrit times, or at least had no distinctive 

 name. In China, as in the Mala} 7 region, Polynesia, and America, 

 yams appear to have been among- the earliest, as the} 7 are still the most 

 important, of cultivated root crops. The Chinese yam {Dioscorea 

 batatas) never penetrated India, has never been reported in the wild 

 condition, and was probabty not a native of the Asiatic continent. 

 Several other species cultivated in India and neighboring regions are 

 also not known in the wild state, and presumably came from farther 

 east. The probability that Dioscorea alata, at least, was carried west- 

 ward by the primitive race which transported the cocoanut is very 

 great, and is supported by the fact that the yam bean (Pachyrhizus), a 

 leguminous plant with a large yam-like root, and of even more highly 

 probable American origin, was introduced in prehistoric times and is 

 still sparingly cultivated in India. In Polynesia the use of Pachyrhizus 

 in religious ceremonies seems to indicate former cultivation, but what is 

 still more interesting, the Polynesians, like the aborigines of America, 

 had knowledge anticipating the modern discovery of the fertilizing 

 value of leguminous crops, and encouraged the growth of Pachyrhizus 

 in their fallow clearings in order to render the land more quickly able 

 to yield good crops of yams. 1 



The sweet potato furnishes another instance of the trans-Pacific 

 distribution of a useful plant in prehistoric times, though it may have 

 come into use later or traveled less rapidly than the cocoanut. In the 

 equatorial belt the sweet potato was doubtless, as it still is, a much less 

 important crop than the yam, but among the subtropical Hawaiians 

 and Maoris it is believed to have been the principal food plant. As 

 with the cocoanut, the sweet potato was designated by cognate names 

 throughout the entire Pacific region, and, moreover, it affords a 

 philological argument wanting with the cocoanut, since the Polynesian 

 names vntara, lumara, 2 and gurnard, are apparently represented on the 

 continent of America by the word eumar, in the language of the Indians 

 of Ecuador. The Mexican name "camote," supposed to have been 

 transferred to the Philippines in Spanish times, may also be derived 

 from the same linguistic root. Like the banana, the sweet potato has 

 become seedless through long cultivation and propagation exclusively 

 from cuttings. The theory of distribution by ocean currents has here 

 no standing; but the botanical evidence of American origin is not 

 nearly as strong as in the case of the cocoanut, since many other 

 species of the same and related genera are very widely spread through 

 the Tropics. Rutland and others have drawn from the names and dis- 



^ngler's Bot. Jahrb., vol. 25, p. 640 (1898). 



2 In addition to this name the people of one of the Viti Islands have a term which 

 means "foreign yam,' - a possible indication of an arrival subsequent to that of the 

 yam. 



