A synopsis of the palms of Puerto Rico

by O. F. Cook

The royal palm is not only the more conspicuous and characteristic 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 several fusiform or clavate bodies from 5 to 10 mm. long and as much as 2 mm. thick. The color of the roots and tubercles is white.

The royal palm of Florida is commonly referred to Oreodoxa regia, though with very doubtful propriety. Apparently on account of its great size, Cooper (Smithsonian Report 1860: 440. 1861) was inclined to identify it with Oreodoxa oleracea which had also been reported from the Bahamas. The inflorescence and seeds collected by Curtis on the western borders of the everglades (no. 2676) are, however, obviously not those of R. oleracea but are much more similar to those of R. regia. The branches of the inflorescence are much longer and more lax than those of the species of Cuba and Puerto Rico, from which they also differ in the frequent development of tertiary branches, in this respect resembling Roystonea oleracea. The fruits do not resemble those of R. oleracea but are closely similar to those of the other species though somewhat smaller and more nearly spherical. Several reliable witnesses are on record to the effect that the trees are from 28 to 35 metres high and as much as 45 metres has been claimed, while among the royal palms of Cuba and Puerto Rico 18 metres is the commonly recognized limit of size. Mr. C. T. Simpson, of the U. S. National Museum, states that the palms of southwestern Florida lack the conspicuous bulge so characteristic in the trunks of the Puerto Ricon trees, and that they grow almost in reach of tide-water, while the natural habitat of the Puerto Rico species is evidently the limestone hills. In view of these differences it seems preferable to treat the Florida royal palm as a distinct species, for which the name Roystonea Floridana is proposed.

Mr. Simpson also informs me that the royal palms seen on the islands off the coast of Honduras had the size and habit of those of Florida and not the relatively stunted appearance of those seen by him in Hayti and Jamaica. This fact is suggestive in connection with the popular idea that the palms of Florida are to be looked upon as recent arrivals from Cuba. Instead it seems more reasonable to believe that the royal palm of Puerto Rico, like the species of Thrinax of that island, is a remnant of the flora of the time when the limestone hills were keys and hammocks like those of southern Florida, and relatively poor in vegetation able to crowd out the palms.

Acrista gen. nov.

Trunk slender, of uniform diameter. Pinnae horizontal, appendiculate. Inflorescences distinctly infrafoliar; spathes two, the outer short, the inner long and slender. Spadix once-branched, the branches coarse, tapering. Fruits with stigma lateral, seed deeply ruminate, embryo basal.

Related to Roystonea, but differing in the more slender habit, the once-branched inflorescence, the basal embryo, and in having the leaflets in one plane. The color of the foliage is also considerably lighter than that of the royal palm so that from a distance the general appearance suggests the cocoanut rather than the royal palm.

There is also some resemblance between the foliage of Acrista and Cocops, but the absence of sheathing leaf-bases in the latter genus will enable even young specimens to be separated. Moreover the leaf-divisions of Cocops are much narrower and those at the end of the leaf are not so much shortened as in Acrista.

Further differences from Roystonea are to be found, such as the much smaller size and the larger roots, which are tuberculate and inclined to become superficial like those of the llume palm. The sheathing leaf-bases are not as long proportionately as in Roystonea, and there is a distinct formation of fibers, although the texture is flimsy. The outer sheaths do not split off and fall away as promptly as in Roystonea but several dead ones sometimes hang from about the base of the crown. Although the sheath is longer than in Aeria the fibers are much better developed, there being but a few membranous shreds in Aeria, and no distinct fibers at all.