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 Bican mountain palm (Acrista moniicola) were 

 found in great numbers near Utuado, Porto Rico, in July, 1901, in 

 one of the dense forests of tabonuco (Dacryodes Jiexandra) 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. a 



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 



a The Porto Rican mountain palm was described as a new genus in 1901. (0. F. 

 Cook, A synopsis of the palms of Porto Rico, Bulletin of the Torrey Botanical Club, 

 vol. 28, p. 555.) For a photograph of the tabonuco forest in which the seedling palms 

 occur, see Cook , O . F . , and Collins, G . N . , Economic Plants of Porto Rico, Contributions 

 U. S. National Herbarium, vol. 8, p. 132, pi. 34. (1903.) 



