CLIMATIC LIMITATIONS. 273 



tribution of the sweet potato arguments for Polynesian contributions 

 to prehistoric America; but if the present interpretation of the history 

 of the cocoanut be accepted it will afford additional support for the 

 opinion shared by De Candolle that the sweet potato is of American 

 origin and was carried by man from east to west. But, without 

 attempting- here an exhaustive discussion of the nativity and history 

 of either the sweet potato or the banana, it is sufficient to reiterate 

 that the existence of these two seedless plants on both sides of the 

 Pacific in prehistoric times goes far to demonstrate former human 

 communication by means of more extensive land masses or, through 

 greater nautical skill, across seas commonly deemed impassable to 

 primitive man. 



THE DISSEMINATION OF THE COCOA PALM. 



At the present time the cocoa palm is to be found on nearty all 

 tropical coasts, though there are still many hundreds of miles of shore 

 line in Africa and Australia not yet adorned by this magnificent plant. 

 Of the few subtropical countries, where the species has been grown 

 successfully, southern Florida is perhaps the most important; for 

 while the tree is able to thrive in a great variety of soils, and even in 

 pits dug in solid limestone, it is apparently very susceptible to injury 

 from extremes of temperature, and is incapable of being naturalized 

 in regions subject even to moderate cold, or in those where great heat 

 must be endured. But, like many other palms, it will, if planted, 

 vegetate for many years in situations where fertile seeds are never 

 matured. 



Being thus strictly limited to the Tropics the habits and conditions 

 of growth of the cocoa palm have received comparatively little atten- 

 tion from the botanical writers of temperate regions. Although, as 

 already indicated, it is probable that the cocoa palm was not dissemi- 

 nated in the Atlantic Ocean until after the Spanish discovery of 

 America, its rapid extension in the Western Hemisphere, together with 

 the fact that it was found to be so widely spread in the East, seem to 

 have been taken as indications that its distribution has been extended 

 by natural causes. But while it evidently existed much earlier in the 

 East Indies, there is some ground for the opinion that its arrival 

 in Asia was comparatively recent, or subsequent to the development 

 of a considerable degree of civilization in the countries bordering on 

 the Indian Ocean; and even in Mohammedan times there is said to 

 have existed a brotherhood devoted to the dissemination of the cocoa- 

 nut among the islands of this region. In Ceylon there is an extensive 

 and well-preserved tradition x implying a rather late introduction of 



^eeman's Popular History of the Palms, p. 146 (London, 1856). 



