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 nearly 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 ina 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! implying a rather late introduction of 
1Seeman’s Popular History of the Palms, p. 146 (London, 1856). 
