302 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
tolerant of shade the conditions would seem to be most. effectively 
arranged for bringing this about, but very little progress appears to 
have been made, in spite of the most rigorous and persistent selection 
that could well be imagined. 
Many other palms are able to germinate in places where there is 
not light enough to enable them to grow to maturity. The seedlings 
may be reckoned as shade tolerant during the early period, while they 
can draw upon the nourishment stored in the seed, but without 
access to direct light they never complete their development. Young 
seedlings of the Porto Rican mountain palm (Acrista monticola) were 
found in great numbers near Utuado, Porto Rico, in July, 1901, in 
one of the dense forests of tabonuco (Dacryodes hexandra) that still 
crown the summits of a few of the mountains of that island. The 
young palms grow thickly over large areas, forming almost the sole 
undergrowth of the forest. Yet in spite of the vast numbers of seed- 
lings not a single adult palm could be seen. The seeds of the moun- 
tain palms are said to be brought into the forest by wild pigeons that 
prefer the lofty tabonuco trees for roosting places.4 
The African oil palm presents similar facts. The seedlings are 
tolerant of shade and very tenacious of life. They are found in vast 
numbers along the paths in the forests where the seeds are dropped 
by the natives, who commonly use the fruits as food on their journeys. 
But in spite of the vast numbers of seedlings, mature oil palms are 
never found in the forest belt, except where natives have cleared the 
land for rice or cassava. It is easy to understand why oil palms are 
much more abundant in regions that support large native populations, 
as in Dahomey. The more frequently the land is cleared the greater 
the advantage of the oil palms over other forms of vegetation. 
In their relation to external conditions the whole natural order of 
the palms can be divided into two distinct series, those that are toler- 
ant of shade and those that are not. Many species of small palms 
live as undergrowth in the shaded depths of tropical forests, and are, 
in nature, strictly confined to such situations. The forests of tropical 
America afford numerous examples of undergrowth palms among the 
species of Chamaedorea, Geonoma, and related genera. All of the 
large palms, those that attain the dimensions of trees, require exposure 
to the sunlight in order to complete their development. 
The palms may have been more prosperous in some former geologic 
time, but the competition of more modern and efficient types of vege- 
tation now confines them to situations relatively unfavorable for 
@The Porto Rican mountain palm was described as a new genus in 1801. (O. F, 
Cook, A synopsis of the palms of Porto Rico, Bulletin of the Torrey Botanical Club, 
vol. 28, p.555.) Fora photograph of the tabonuco forest in which the seedling palms 
occur, see Cook, O. 1. and Collins, G. N., Economic Plants of Porto Rico, Contributions 
U.S. National Herbarium, vol. 8, p, 132, pl. 84. (1903.) 
