Palms of Puerto Rico 553 



when dry they still appear somewhat longer and larger than the 



latter. 



The seeds of Roystonca Borinqucna differ in several particulars 

 from those of the Cuban species. In shape they are longer and 

 less spherical, measuring 8 by 6.3 by 5.5 mm. instead of 7.8 by 

 7 by 6 mm. ; the side bearing the hilum is much flattened and 

 even slightly concave ; the fibers radiating from the hilum are 

 longer, and the corner between the hilum and the micropyle is 

 evenly rounded, not sharply squared and prominent as in A\ regia. 

 On the back of the seed the smooth inner wall of the endocarp is 

 closely adherent over a small area, while in Cuban seeds this wall 

 remains attached over nearly the whole side and is furthermore 

 distinctly rugose-coriaceous on the surface, and has a distinct sul- 



cus in the median line. 



The royal palm is not only the more conspicuous and charac- 

 teristic natural object in most parts of Puerto Rico, but it probably 

 exceeds the cocoanut in total economic importance. The most 

 useful part is the yagua or sheathing base of the leaf, with which 

 a large proportion of the houses of the poorer classes are thatched 

 or sided, or both. 



The royal palm is one of the wild species which has been 

 distinctly advantaged by human interference in natural conditions. 

 It is a general fact that outside the climbing species palms are not 

 successful in competing with tropical forest vegetation. Originally 

 the royal palm and the corozo were probably confined to the 

 more rugged slopes of the lower limestone hills where they both 

 still retain a foothold in places where the natural growth seems 

 never to have been cleared away. But the vast majority of royal 

 palms now in existence in Puerto Rico stand on land which has 

 been cultivated at one time or another, and where the palms were 

 able to secure a foothold before the competition of other plants 

 became too strong. 



The discovery of root tubercles on a young plant of this species 

 has been noted in the introductory statement. These tubercles 

 though small in size are very numerous upon the smaller roots. 

 In shape they are mostly oval and symmetrical. The larger are 

 about 2 mm. in length though our natural-size photograph shows 



•dies from 5 to 10 mm. long and as 



S u " «-""-fc, 



