282 ORIGIN AND DISTRIBUTION OF THE COCOA PALM. 
yet the banana is seldom, if ever, able to establish itself as a wild 
plant in tropical lowlands, for the reason that wherever it will grow 
shrubs and trees will also thrive and choke it out in a few years. 
The case is much the same with the cocoanut, except that in the course 
of a century the signs of human agency would more effectively dis- 
appear. It is not sufticient to find cocoa palms far from existing 
human habitations: the question is whether the species could really 
maintain itself without human assistance and protection against other 
vegetation. Obviously this can not be determined by simple inspec- 
tion, but a satisfactory experiment might require careful records car- 
ried over at least two or three generations of men and palms. The 
probabilities are, however, overwhelmingly against the continued 
independent existence of the cocoa palm at sea level anywhere in the 
moist Tropics. It is true that if planted by man it will grow in many 
places where it would never plant itself, and it might also maintain 
itself in places where the proper conditions were continued by human 
agency. In undisturbed nature, however, the extermination of the 
cocoanut by the encroachment of the tangled masses of vegetation 
which invade tropical beaches would probably require but a few cen- 
turies. This idea is recognized in the Cingalese proverb, ** The cocoa- 
nut will not grow out of the sound of the sea or of human voices,” and 
in the belief held among the same people that the trees will not thrive 
unless ‘S you walk and talk amongst them.” 
Although the cocoa palm furnishes an extreme instance, this require- 
ment of open ground is not peculiar to it, but is general in this entire 
natural order, the members of which, with the exception of the climb- 
ing genera, are unable to survive under genuine jungle or forest 
conditions. The large, long-leaved spec ies are particularly at the 
mercy of tangled tropical vegetation, since it is impossible for them 
to make the rapid growth necessary to keep up with trees of other 
plant families. The arboreal palms are first required to produce a 
long succession of leaves at the level of the ground, their trunks 
making no upward growth until the full diameter has been reached, 
which seldom requires less than three years. On completely barren 
islands ' seedling cocoanuts might continue to flourish, but if the space 
‘Dr. Treub has reported (Ann. Jard. Bot. Buitenzorg, vol. 7, p. 217, 1888) the find- 
ing of a cocoanut on the beach of an island formed by the eruption of Krakatoa, but 
no intimation is given that it had germinated or was alive. 
The very small and remote Keeling Islands of the Indian Ocean offer, perhaps, the 
most probable instance of spontaneous occupation by the cocoa palm, but even here 
the assertion of the absence of human agency is limited to the denial of ‘permanent 
inhabitants”’ earlier than the nineteenth century. Moreover, there seems to have 
been but one other arboreal species ( Cordia subcordata) which has become numerous, 
and this was confined to the interior of the islands, leaving the coast districts to the 
uncontested monopoly of the cocoanut. These islands have been studied by Darwin, 
Forbes, and Guppy, and the last mentions (Journ. Trans. Victoria Inst., vol. 24, 
