Palms of Puerto Rico 537 



session, but on many of the drier and more sterile higher slopes 

 the advantage is with the palms. 



This abundance of living; material deserves more careful 

 study than could be given during a very brief visit to this al- 

 most uninhabited part of the island, but one note of systematic 

 interest was made. Several species of Thrinax, of which T. Mor- 

 risii Wendland may serve as an example, have been described 

 chiefly with reference to the relative size of the leaf segments and 

 the extent of their separation. If the palms under observation 

 near Ponce belonged, as was believed, all to one species, it is not 

 only true that the individual Thrinax passes all the stages from 

 the narrow and grass-like, almost completely separated segments 

 of the very young plant, to the more than half united leaf of the 

 large tree, but it also appears to be true that under unfavorable 

 conditions a Thrinax may not be able to attain to full maturity of 

 size and form but may at the same time produce flowers and seeds. 

 In the narrow chinks and crevices of the bare rocks were very 

 small, stunted trees, obviously of great age, while but a few feet 

 distant a deeper fissure might hold vegetable debris and moisture 

 sufficient to nourish vigorous specimens several times the size of 

 their less fortunate companions. The stunted trees retain in pro- 

 portion to their size, but apparently with little reference to their 

 age, the small deeply divided leaves of young plants and have 

 short few-branched inflorescences, another difference of supposed 



systematic importance. 



In Thrinax Ponceana the leaves of well grown trees have the 

 middle divisions united to about the middle; the smaller the leaves, 

 the more deeply they are divided. A further correlation with size 

 is that of the "fullness " o( the leaf. The basal sinus is not closed 

 by the overlapping of the lateral divisions as in some species, but 

 the area is too great for a plane circle and there are one or more 

 folds, more numerous and deeper in large leaves. The lateral 

 divisions do not lie in the plane of the others but project upward 

 or backward nearly at right angles with the plane of the middle 

 divisions. 



The middle divisions of large leaves may measure 75 cm. in 

 length by 3.5 and sometimes nearly 4 cm. in width, while the nar- 

 rowly grass-like lateral segment is only .8 cm. wide and about 30 



