Part 5

7. The veinules of the firm leaves of Thrincoma are more numerous and closer together than those of Thrinax.

8. The veinules are also subequal in size, giving an appearance of uniform pattern, while in Thrinax praeceps from 3 to 5 of the veinules of each side of the midrib are distinctly larger than the others, the larger veinlets being separated by from 3 to 10 smaller ones.

9. In Thrincoma the cross-veinules are scarcely visible to the naked eye; under a lens they are still obscure, never equalling in size the smaller of the longitudinal veinules, which they seldom appear to cross. In Thrinax praeceps, on the contrary, the cross-veinules are as large as the finer longitudinal ones; they are obvious without a lens and give the fabric of the leaf a peculiar marbled effect on account of the fact that they are generally oblique or wavy and commonly appear to cross several of the longitudinal veinules.

10. The margins of the segments are thickened in both species, and on the upper side there is a groove inside the marginal rib. In the short species the margin is flat below and does not become decurved in drying. In the other the thin edge is closely folded under, and on drying the sides of the segments uniformly roll under, giving the dried leaves of the two species an appearance even more dissimilar than in the fresh state.

11. The lower surface of the leaf of Thrincoma has a silvery white layer of fine closely appressed hairs, all lying parallel to the veins and forming a continuous covering. The fibers seem not to be attached merely at one end, but along the side. They are firmly adherent and are to be removed only by scraping or rubbing; the surface underneath is deep green like the upper side, but the fibers remain in the grooves between the veins. In Thrinax praeceps the lower surface of mature leaves is smooth and glaucous, a comparatively very slight hairy covering present in young leaves being evanescent, though traces of it are usually to be found in the deeper basal grooves. The glaucous appearance is due to the presence of numerous white or hyaline points arranged in rows (stomata?). The hairiness of one leaf and the glaucous character of the other are probably to be looked upon as different adaptations for the same purpose—the reduction of transpiration.

12. The upper surface and the ligule of young leaves of Thrincoma are covered with a layer of wax in the form of small plates or scales not present in Thrinax.

=Thringis= gen. nov.

Trunk columnar, rimose; wood pithy. Leaves coriaceous with equal veinules, silvery below with closely appressed whitish pubescence. Fruits distinctly pedicellate, the pedicel with a bract above the base. Seed cerebriform, irregular, with wide furrows and convolutions; surface smooth and shining. Embryo subapical.

The characters of this genus are imperfectly known, none of the specimens being complete. Supposing however, that the association is a natural one, we have a genus with leaves and pedicellate fruits much more similar to those of Thrincoma than to those of Thrinax, and at the same time a columnar, rimose and pithy trunk like that of Thrinax and Coccothrinax. The seeds appear to differ from those of all related genera in the possession of large irregular convolutions. The coriaceous leaves, small fruits, subapical embryo, and other differences separate this genus from Coccothrinax.

=Thringis laxa= sp. nov.

The trunk is columnar or somewhat enlarged upward, about 3.6 m. high and 12 cm. in diameter. Surrounding its base was a dense turf of fine upright rootlets. The bark was rough and rimose.

The leaves are similar to those of T. latifrons, but smaller, the segments being about 70 cm. long by 33 mm. wide. The size of leaves is thus about the same as those of Thrincoma alta, but the texture is thin and flexible, the veinules being slender and not prominent on either side. The pubescence is much thinner than that of T. alta and of a silvery-gray color.

A palm collected in December, 1899, at Vega Baja, but without fruit (no. 1041). The habit and trunk are not those of Thrincoma, but the form and texture of the leaves and ligule associate the species with Thrincoma alta rather than with the palms here placed in Thrinax.

The columnar habit and protected habitat are reflected in the small ligule, 18 mm. across, and the relatively broad petiole, 13 mm. wide. It appears from the dried specimens of this species and T. latifrons that the leaves may have been “full,” or irregularly folded, instead of strictly and equally expanded as in Thrincoma alta, and the greater width of the segments is a further indication of this possibility. The rigidity of the leaf of Thrincoma alta can be maintained because the segments are narrow and do not open widely.

The soft texture of the leaves of this palm is recognized by the natives who use it for making hats and call it “yaray” the same name which is applied in this part of the island to Inodes causiarum.

=Thringis latifrons= sp. nov.

The leaves, inflorescence and young plants of a palm collected by Sintenis (no. 3278) on Monte Calabaza near Coamo are much larger and coarser than those of Thrincoma alta. The total length of the middle segments of the leaf would be over a meter, and the width of the larger divisions is over 5 cm. The thickness of the petiole at the base of the ligule is over 10 mm. The form of the ligule is much like that of Thrincoma alta, though scarcely as large in proportion to the size of the leaf.

The lower surface is clothed with a satiny, appressed grayish pubescence somewhat less pronounced than that of Thrincoma alta. As in that species the veinules are of equal size, but they are more widely separated, and the wavy and usually somewhat oblique transverse veinules are easily distinguishable on both sides of the dried leaf. There are also slight traces of wax on the ligule and in the grooves of the upper surface. The median divisions are united for distinctly more than one-third their length.

The spathes and spadix are distinctly larger than those of Thrincoma alta, but the fruits are, unfortunately, quite immature and contain only shriveled seeds. The pedicels of the fruits are 2–4 mm. long and bear, usually near the middle, a very slender bract 1–2 mm. long.

This species is apparently distinct from Thringis laxa in the larger size and firmer texture of the leaves. It differs in the longer pedicels of the fruits, with their longer and more slender bracts, from a specimen belonging to the New York Botanical Garden and supposed to have been collected by Mr. A. A. Heller, though the number (3278) indicates that it may belong to the Sintenis series.

This consists of a single, short, once-branched inflorescence arising from two fibrous spathes. The fruits are about 4 mm. in diameter, nearly spherical, distinctly apiculate, deep reddish brown in color and borne on pedicels 2–3 mm. long, with a bract 1 mm. long or less at or below the middle. The seeds are 2–2.5 mm. in diameter; the surface is smooth and shining and light brown in color; general shape spherical but with deep folds and convolutions.

No leaves are known in connection with this specimen, and the exact locality is also in doubt. Mr. Heller believes, however, that the inflorescence came from a small Thrinax-like palm growing in the limestone hills a few miles to the east of San Juan.

Family ARECACEAE

A large family, with abundant genera in the tropics of America and Asia, but absent from tropical Africa. The Puerto Rico representatives may be recognized very easily by the fact that the leaf crown is supported upon a column of the sheathing bases, a character of which the royal palm furnishes a conspicuous and ever-present example. Of the remaining genera, one, the betel palm of the East Indies is sparingly introduced about towns in the western part of the island and may be recognized at a glance by reason of the extremely dark green of its foliage. The other two genera are native palms confined to uncultivated areas and thus seldom seen at close range from traveled roads. The mountain palm, Acrista, covers the summits of many of the mountains of the island, but Aeria seems to be confined to the range of high limestone crags which skirt the northern coast of the island between Bayamon and Arecibo.

Key to the Genera of Arecaceae

Trunk tall and slender, tapering from a swollen base; spathes numerous (7); inflorescence appearing in the axis of the rather persistent lower leaves, long and slender; staminate flowers arranged in rows.

AERIA.

Trunk robust or of uniform diameter; spathes 1 or 2; inflorescence short and brush-like, not exposed until the enclosing leaf below it falls away; flowers not set in rows.