A synopsis of the palms of Puerto Rico

by O. F. Cook

Family SABALACEAE

Although forming no conspicuous part of the palm vegetation of the island the fan-leaved species seem to be more numerous than those of any other family. It is certain also that further species remain to be discovered, since in addition to the species listed below, young inflorescences supposed to belong to a Copernicia were collected by Sintenis (no. 6512) near Utuado, and he also collected two other Thrinax-like palms of doubtful identity, one near Cabo Rojo and one at Fajardo.

Key to the Genera of Sabalaceae

Leaves depressed in the middle, with a distinct decurved midrib; a slender fiber rising from each of the notches which separate the leaf segments.

Inodes.

Leaves flat, midrib rudimentary; segment without alternating fibers.

Leaves chartaceous, naked on both sides when mature, the veinules unequal; fruits nearly sessile; seeds smooth, albumen solid except for a deep basal cavity.

Thrinax.

Leaves tough and coriaceous, the lower surface silvery with a persistent, closely appressed pubescence; veinules equal; fruits distinctly pedicellate; seeds deeply grooved or furrowed.

Trunk tapering upward, tall and slender; pedicels short, bracteate at base; seeds subspherical, ruminate with deep narrow grooves; surface with a dull membranous cuticle.

Thrincoma.

Trunk columnar, of equal diameter or enlarged upward; pedicels long, bracteate above the base; seed naked, smooth and shining, cerebriform, the surface irregular with broad furrows and convolutions.

Thringis.

Inodes gen. nov.

In this genus, of which the hat palm of Puerto Rico may be considered the type, it is proposed to accommodate the dendroid palms commonly referred to Sabal, the type of which is S. Adansonii Guersent. The most conspicuous difference between Inodes and Sabal is, of course, the fact that the former produces an upright trunk while the latter has only what might be called an underground rootstock, although such a distinction is quite artificial, both groups of species beginning life with a creeping axis which becomes erect in one and remains horizontal in the other. A much more important difference is to be found in the leaves which in Inodes have secured strength by the development of a midrib, a tendency early abandoned by Sabal in which the midrib is rudimentary and the middle of the leaf is the weakest part. The leaves of Sabal are adapted for standing erect and avoid resistance to the wind by being split down the middle. The leaves of Inodes which are held horizontal from an erect axis have attained the unique adaptation of a decurved midrib which braces the sloping sides of the leaf and effectively prevents the breaking above the ligule common in some of the species of Thrinax. It is true that leaves of young specimens of Inodes stand erect like those of Sabal and do not have the curved midrib, but even at this stage the midrib is relatively well developed and the blade opens out to an almost circular form instead of occupying an arc of 180 degrees or less as in the more strictly flabellate leaves of Sabal.

Further differential characters might be enumerated, such as the short ligule and the flat petiole of Sabal. The inflorescence and seeds also afford differences, but these points are unnecessary for diagnosis, and their proper expression will require careful comparative study of the species of both genera, since Sabal is not monotypic but includes at least two species from the Southern States and perhaps S. Mexicana Martius. Guersent’s S. Adansonii, the first binomial species to which the name Sabal was applied, is, to judge from the figure, the smaller of our species, while Jacquin’s Corypha minor may be the larger. Both species were described from hothouse specimens and the plates give no details really adequate for identification, but if there are but two species to be considered there can be little doubt that Jacquin’s drawing represents the larger of the two forms commonly referred to Sabal Adansonii, since the leaves are nearly four feet long with the mesial divisions united somewhat less than half way up. The basal segments are represented, however, as diverging horizontally and not obliquely as is usual in the living plants in the greenhouses of the Department of Agriculture.

Guersent maintained that he was dealing with the Sabal which Adanson had in mind in naming the genus, and made his specific name in accordance with that fact, treating Corypha minor Jacquin, Corypha pumila Walter and Chamaerops acaulis Michaux as synonyms. The relative merits of these names and of Chamaerops glabra Miller, which Dr. Sargent (Silva, 10: 38) has resurrected, are not likely to be easy of determination, but since the last was based on plants grown from seeds which came from Jamaica, it seems unwise to use it for United States species to which the description is inapplicable. Miller’s name may, however, replace Sabal taurina Loddiges which was also founded on a stemless Sabal supposed to come from Jamaica.

The species of Inodes are in a similar or even worse state of disorder. There is little use, for example, in transferring to the new genus the traditional name umbraculifera which was based by Martius on the Corypha umbraculifera of Jacquin, but not on Linnaeus’ species of the same name, which is a native of Ceylon. Present taxonomic methods forbid such generic transfers of misapplied names, so that the name Inodes Blackburniana (Sabal Blackburniana Glazebrook, Gardener’s Mag. 5: 52. 1829) should be used instead of the traditional Sabal umbraculifera of the conservatories, though the identity and origin of the species still remain in doubt.

Inodes causiarum sp. nov.

Trunk 45–75 cm. thick at base, 5–15 m. tall, columnar or slightly tapering upward; surface narrowly rimose or nearly smooth, light gray or nearly white. Leaf-bases splitting into rather brittle fibers, partly remaining compacted into long ribbons 5–8 cm. wide. Leaves about 4 m. long, the petiole subequal to the blade, considerably exceeded in length by the inflorescence. Petiole 3.8 cm. wide, distinctly carinate above near the end; ligule 4.2 cm. in diameter. Fruit grayish, 9–10 mm. in diameter; seed chestnut-brown, finely rugose or nearly smooth, 7–8 mm. in diameter; embryo oblique, at an angle of somewhat less than 45 degrees from the horizontal. Type specimen from Joyua (no. 154).

The palm-leaf hats manufactured in large quantities in Puerto Rico are made from the present species. The center of the hat industry is at Joyua, a small village on the western coast of the island some miles southwest of Mayaguez and west of Cabo Rojo. Here many hundreds of the palms are growing along the shore in a narrow belt of coral sand.

From the two species of Sabal recognized by Grisebach Inodes causiarum differs from umbraculifera in having the inflorescence much longer than the leaves, while the trunk and leaves are much shorter and thicker than in Sabal mauritiiformis a native of Trinidad and Venezuela which appears from Karsten’s figure, reproduced in the Natürlichen Pflanzenfamilien, to have neither the leaves nor the habit of an Inodes though there is no other genus to which it can be referred with greater propriety. The diameter of the trunk of the Trinidad palm described as S. mauritiiformis is given as from 12 to 15 inches, while I. causiarum is often two feet or more thick.

From the Florida palmetto, Inodes Palmetto (Corypha Palmetto Walter, Fl. Carol. 119. 1788) the Puerto Rico species differs most conspicuously in not retaining the old leaf-bases which give the trunk of the Florida palm so rough an appearance. The cause of this difference is doubtless to be found in the fact that as with most other palms the trunk of I. Palmetto grows to full size while the surrounding leaf-bases are still alive, but in the West Indian species the trunk tapers greatly, especially in young trees, and the leaf-bases are torn away by its gradual enlargement to full diameter. The existence in southern Florida of an Inodes having this last characteristic is a fact of much interest recently brought to my attention by Mr. E. A. Schwarz, of the U. S. Department of Agriculture. The specific distinctness of this palm was impressed upon Mr. Schwarz, not only by its naked trunk, different habit, and smaller size (5 m., instead of 10 to 20 m.), but also by the possession of a distinctly tropical insect fauna, quite different from that of the more northern palmetto with which he had previously been familiar.[^[2]]

This new Florida species it gives me pleasure to name Inodes Schwarzii in honor of its discoverer, in whose opinion of its distinctness I have great confidence, although he makes no claims to botanical skill. It is confined, as far as observed by Mr. Schwarz, to the coral reef formation of southern Florida, the most accessible station visited being about one mile south of Cocoanut Grove on the coral reef of the mainland side of Biscayne Bay. In the vicinity of Snapper Creek, Inodes Schwarzii extends to the Everglades where it is met by I. Palmetto. It was also seen on the Perrine Grant about six miles from Cocoanut Grove; it seemed not to occur about Miami but reappeared with the appropriate formation and attendant fauna at New River, though again absent at Lake Worth. A photograph secured by Mr. H. J. Webber (negative 164) on Taby Island near Long Key shows an Inodes with a naked trunk and a smaller crown of straighter leaves than are normal for I. palmetto. Messrs. Swingle and Webber had also remarked the distinctness of the smooth-trunked palmetto of South Florida.

A third robust species of Inodes is growing in the conservatory of the Department of Agriculture labeled Sabal umbraculifera. It differs conspicuously from I. causiarum by the very large leaves and by the great development of fine brown fibers which fill all the interstices between the leaf-bases, and suggest the name Inodes vestita.[^[3]] Photographs of both the species have been prepared for the illustration of comparative detailed descriptions.

Sabal Mexicana has been reported from Cuba, and as it is described in Sargent’s Silva (10: 43) as having a trunk “often 2½ feet in diameter,” a robustness equalled only by the Puerto Rico trees, the question of its identity was examined. It appears that the original of S. Mexicana came from southern Mexico and is a trunkless or very slender, rather than a robust species, being only about 10 cm. in diameter. The berry and the seed are described as closely similar to those of Sabal Adansoni. Sargent’s S. Mexicana from southern Texas, in addition to the seven times greater thickness of the trunk, has a seed nearly 1.25 cm. broad with a strongly prominent micropyle. There can be little doubt that it is another new species, quite distinct from that of Puerto Rico, similar only in the unusual diameter of the trunk, which is furthermore described as bright reddish brown instead of white or very light grayish as Inodes causiarum. In the view of the apparently localized distribution of the species of this genus the name Inodes Texana would be appropriate for that described and figured by Sargent as noted above.

In addition to the recently described Inodes Uresana (Sabal Uresana Trelease, Rep. Mo. Bot. Gard. 12: 79), there is another large-seeded Inodes on the western slope of Mexico, a specimen of which was collected at Acaponeta, State of Tepic (no. 1528) by Dr. J. N. Rose,[^[4]] for whom this species may be named Inodes Rosei. The seeds are of the same size and shape as those of I. Uresana, but have the surface much more finely rugose, or nearly smooth, with the embryo directly lateral, not subdorsal. The branches of the inflorescence are slender and but little over 1 mm. in diameter instead of fusiform and thickened in the middle to nearly 3 mm. as shown in Professor Trelease’s photographic illustration.

THRINAX Linn. f.; Swartz, Prod. Veg. Ind. Occ. 51. 1788

In the genus Thrinax were formerly placed all the West Indian fan-palms with smooth stems and no midribs, but the gradual discovery of numerous and diverse species has resulted in propositions for subdivision and segregation on the part of several botanists. As usual these new groups have been characterized very inadequately, and that mostly from the flowers and seeds, and with no attempt at establishing correlations of habit or other vegetative features without which the classification is likely to remain formal and artificial, as well as useless for popular and field study. Possibly no ecological differences exist among the Thrinax-like palms of other regions, but in Puerto Rico there are, as shown in the discussion of the following genus, two well-defined types, one of which varies the ordinary short columnar habit by the possession of a tall slender and flexible trunk which doubtless enables it to compete in a measure with the rapid growth of the surrounding vegetation, and which is also obviously adapted for withstanding the force of the strong winds encountered in the exposed places apparently preferred by palms of this species.

The type of the genus Thrinax is the Jamaican T. parviflora, a tree 3 to 6 metres high with the trunk swollen at base. The leaves are said to be 30–60 cm. long with rigid lanceolate divisions; the stipes longer than the leaves, terete-compressed. The spadix is said to be terminal, nearly erect and 60–90 cm. long. The tree grows in dry maritime situations in Jamaica and Santo Domingo. It does not appear that the original specimens of this species have been examined by Sargent or other recent writers, but it seems reasonable to use the name for the group of short species with uniform albumen and a basal cavity instead of a complete perforation. Swartz’s statement regarding the seed “intus albus, medio ruber,” in connection with its context “nauco osseo fragile tectus” might possibly be rendered “white inside, red between” and might refer to the red coat of the seed rather than to a red center as commonly inferred. Of course Swartz might have cut his seed transversely, but if so he would doubtless have discovered and noted the perforation had one existed. Patrick Brown’s account of the Jamaica species, cited by Swartz, evidently refers to a palm with the habits of T. Ponceana. On the other hand the “very slender” palm referred to under this name in the Jamaica Bulletin (I: 196. 1894) shows greater similarity with Thrincoma.

Thrinax praeceps sp. nov.

Trunk 8–12 cm. in diameter at base, columnar or slightly enlarged upward, seldom attaining over 3 or 4 meters in height. The leaf-bases split in the middle of the midrib and long remain adherent to the trunk. When they finally fall away on older trees a rather rough grayish and longitudinally chinked rimose surface is exposed.

The stalks of large leaves measure 75–80 cm. in length and 1.2–1.5 cm. in width. The middle divisions of the leaf are 55 cm. and under in length and attain a width of 4.8 cm., and in the middle of large leaves are united for more than half their length. Cross-veinules numerous, distinct in both surfaces but especially the upper. The white pubescence or tomentum which clothes the young leaves and is especially abundant on the ligule soon disappears, leaving the under side glaucous or slightly pruinose.

This species is described at some length a little later in a comparison of generic characters under Thrincoma alta. The type specimen (no. 850) was collected on the precipitous mountain-side which overhangs the road between Utuado and Arecibo, a short distance to the northward from the station where Thrincoma alta was obtained.

What is believed to be the same species was collected in a similar situation on the side of a mountain overlooking the town and valley of Lares.

Thrinax Ponceana sp. nov. [Plate 43]

Trunk 5–8 cm. or more in diameter, columnar, or slightly tapering or enlarged upward, 1–4 m. high; surface coarsely and irregularly rimose longitudinally. Leaf-bases separating into abundant rather loose light grayish or brownish fibers. Leaves numerous, large, drooping or pendant; petioles 65 mm. long, 1.5–2 cm. wide; segments attaining 75 cm. in length and 3.5 cm. in width, united for half their length. Seed smooth, mahogany-brown, 5 mm. in diameter. Type specimen no. 1005.

This species apparently exists in much larger quantities than any other yet known from Puerto Rico, being the predominant plant on several square miles of territory along the range of dry limestone hills which skirt the southern coast of the island, to the west of Ponce. Many of the palms are scattered among the taller shrubs and trees wherever there is sufficient soil and water to permit these to grow and yet not enough to give them exclusive possession, 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 almost uninhabited part of the island, but one note of systematic interest was made. Several species of Thrinax, of which T. Morrisii 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 débris and moisture sufficient to nourish vigorous specimens several times the size of their less fortunate companions. The stunted trees retain in proportion 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” of 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 narrowly grass-like lateral segment is only .8 cm. wide and about 30 cm. long. The lowest segment is not divided at the tip but is produced into a slender hair-like seta, 6 or 8 cm. long, making it nearly as long or longer than the next segment above.

The normal segments are split at the apex to the distance of from 2 to 8 cm. and the tips are usually markedly divaricate, owing to the fact that the young leaves of this species suffer two impressions from the bases of older leaves, one near the middle, the other near the end. The pressure causes the curvature of the unopened leaves, which in turn causes them to split apart when the leaf expands.

Old leaves are smooth and glaucous on the lower side, but in the younger state more or less remains of the delicate appressed hairiness present on the lower surfaces of the newly opened leaves. The lower surface is distinctly grayish and glaucous, but under a lens it can be seen that this appearance is due to the presence of numerous whitish points (stomata?) among which are scattering brownish spots of larger size, the nature of which remains a question.

The free stalks of the largest leaves attain 65 cm. in length and are 2 cm. wide near the base, 1.5 cm. near the apex. The cross section is lenticular above, but the upper surface becomes flat toward the base.

Young unopened leaves are covered near the base, both above and below, with a scurfy white tomentum and the margin of the ligule has a long white fringe.

To avoid possible error it seems best to make separate entry of the following notes on specimens which might be considered quite distinct from the larger and normally mature form of Ponceana, but which represent, it is believed, merely a somewhat depauperate condition of that species, although leaves exactly comparable were not brought home by our party. The specimens in question were collected by Sintenis (no. 3500) on the south coast of the island near Guanica and distributed from Berlin as “Thrinax n. sp.”

The leaves are characterized by the narrow straight-sided segments which retain the same width (15 mm. or less) for about 11 cm.; they are united in the middle of the leaf for about 8 cm. and the apical tapering part is about the same length. Other species, so far as known, have the segments much broader, both absolutely and relatively, and the width is held for a very much smaller proportion of the length.

In addition the midrib is unusually weak, inconspicuous and only slightly prominent on the lower side. The small fibro-vascular bundles which compose it are sometimes spread apart so that there is scarcely an indication of a rib while in other segments of the same leaf, and especially at the base, the conditions are more normal. The midrib is sufficiently distinct above, though very small and fine in comparison with other species.

Lower surface of leaf glabrous or somewhat glaucous, very slightly puberulous on the depressed veins near the base. Veinlets inconspicuous, mostly subequal, though 4 or 5 are sometimes a little larger than the others. Transverse veinlets indistinct below.

Petiole slender, 4 mm. wide, lenticular in cross section; about 2 mm. thick. Ligule small and weak, short, with a small apical mucro.

Fruits 5 mm. in diameter, olive brown, irregularly rugose-coriaceous on the outside as though dried from a pulpy condition; exocarp with a slightly sweetish taste. Seed bright mahogany-brown, darker below, depressed-globose, with a sublateral raphe; embryo ascending but more nearly lateral than vertical; conical basal cavity extending somewhat above the center, nearly filled with a deep red material.

At the time of our visit in July no ripe fruits of T. Ponceana were found on the trees, but a few picked up from the ground are apparently indistinguishable from those of Sintenis’ specimen.

Thrincoma gen. nov.

Trunk slender, tapering, flexible; wood firm, covered by a smooth hard brittle outer shell or bark.

Leaf-bases long-sheathing, expanded by the separation of the fibers of the side opposite the midrib; petiole strongly flattened above the base, prominently angled above and below; ligule large and firm, produced laterally to support the outer divisions.

Leaf-divisions narrow, separated below the middle and below the point of greatest width; texture firm and coriaceous; veinules subequal, close together, cross-veinules obsolete. Lower surface clothed with persistent closely appressed hairs, the upper coated with wax when young.

Seeds with few longitudinal grooves, the surface not polished, grayish; embryo subapical.

The generic name alludes to the preference of this palm for the summits of crags and the brows of perpendicular cliffs which abound in the limestone region of the north side of Puerto Rico.

The tall, slender trunk and other differences between this genus and Thrinax are probably to be interpreted as ecological adaptations necessary to enable the present palm to compete with the vegetation which often surrounds its base, and to withstand the winds to which it is commonly exposed. The species of Thrinax and other allied genera, as far as known, have the trunk rigid and columnar, or even enlarged from the base upwards. When growing solitary and exposed they seldom, if ever, attain half the height of Thrincoma. Usually, however, they are protected by other vegetation or by growing gregariously in thickets.

Thrincoma might be described as a Thrinax which has adopted habits of the arecoid genus Acria which grows in similar situations in a neighboring part of the island. In addition to the smooth, slender, and flexible trunk Thrincoma makes further provision against the wind in having fewer, less ample, tougher and more deeply divided leaves and like the arecoid palms it also drops the old leaves as soon as their usefulness is past, instead of retaining, like Thrinax, a large pendant cluster of them. The details of these differences are given below in a comparative note on fresh material of Thrincoma alta and Thrinax praeceps collected but a short distance apart in the lower part of the Arecibo valley along the Utuado-Arecibo road. In this region of jagged mountains, Thrinax seeks shelter against the walls of perpendicular precipices, while Thrincoma challenges the wind and the admiration of the traveller by its evident preference for the crags and pinnacles.

Thrincoma alta sp. nov.

With but one species known with certainty to belong to the present genus the separation of generic and specific characters would have little purpose. Data for a specific description are, however, contained in the following notes which are retained in their original comparative form as better illustrating the generic differentiation of Thrincoma and Thrinax, as represented by Thrinax praeceps.

The trunk of Thrincoma differs in three adaptive particulars from that of Thrinax praeceps, Ponceana and similar species which are merely columnar with very short internodes and an irregularly rimose surface, not smooth and hardened.

1. There are distinct internodes from 3.5 to 5 cm. in length. These indicate rapid growth and would increase the chances of survival in the face of competition of quick-growing tropical vegetation.

2. The trunk tapers gradually from a diameter of 9 cm. near the base to 3.5 at the top, and thus possesses considerable flexibility in view of its great length, 11 meters, Thrinax praeceps and other related types not exceeding 4 or 5 meters.

3. In order to support the weight and strain of this greater height, the texture of the wood is extremely hard and firm, especially near the base of the trunk. Externally it is covered by a smooth shell or bark of very hard, brittle, dark colored material. The fibers of the interior which in Thrinax are merely imbedded in a soft pith like those of a corn-stalk are here thickened and cemented together, as in tall palms of other groups, into a dense hard wood. In the specimen cut by us all but a small area of the middle of the trunk was thus hardened, rendering it extremely heavy. The wood-fibers of Thrincoma are much coarser than those of Thrinax, and there appear to be none of the obliquely radial threads which are abundant in the wood of Thrinax Ponceana.

With reference to methods of leaf-attachment four differences may be noted:

1. In Thrinax praeceps the leaf-bases split below in the median line and remain long attached to the trunk. This adaptation is not confined to the old leaves but appears while the leaves are still very young, or as soon as they begin to be expanded by the pressure of those above them. In the tall species such pressure separates the fibers of the opposite side of the cylinder. The short species has the outside of the leaf-bases densely tomentose, and the tomentum is especially abundant along the edges of the split midrib of the young leaf.

2. The ligule of Thrincoma is notably larger than that of Thrinax and continues to lie in the same plane as the blade, and becomes brown with maturity. In old leaves of Thrinax the ligule stands nearly at a right angle to the blade and remains green.

3. For leaves of the same size the petioles, not including the sheathing base, are longer (75–80 cm.) in the short than in the tall species (60–65 cm.).

The petiole of the short species is of nearly the same width (1.2–1.5 cm.) throughout, while in the other it is distinctly broader at both ends than in the middle. The enlargement at the ligule is abrupt. The base widens gradually to about 2 cm. but is much thinner than in the short species. In the upper part of the petiole the reverse is true, the cross section of the leaf-stalk of the Thrincoma being almost diamond-shape, while that of Thrinax is merely lenticular.

4. These differences of proportion of ligule and stalk are obviously correlated with the different habits of the two species. The shorter and more robust trunk of the one enables it to withstand the strain of the relatively limited exposure to the wind. There is also a greater flexibility in the leaf itself, due to its thinner texture and to the smaller development of the ligule and adjacent thickened area, so that the leaves are often split to near the center. The narrow petiole of the tall species affords greater flexibility in the lateral plane while strength has been secured by the greater thickness. On the other hand the thinness of the base of the petiole of Thrincoma reduces resistance by permitting the petiole to be twisted when the leaf is opposed to the wind or blown laterally, thus avoiding the strain which would come upon the more rigid base of the petiole in Thrinax.

The more salient differences between the leaf-blades of the two species may be enumerated as follows:

1. Although the length of the middle segments of the leaves of Thrincoma are longer (62 cm.) than those of the other (55 cm.) the apparent size of the latter is much greater because they are fully expanded while those of Thrincoma remain more or less fan-shaped, generally opening less than a semicircle. This decreases the lateral expansion, since the shortest divisions are brought to the sides, and gives no projection below the ligule where in Thrinax more than one third of the foliar expanse is located.

2. The leaf segments are much narrower (3.6 cm.) in the tall than in the short species (4.8 cm.).

3. Practically the difference in width is still greater because the segments of Thrincoma are never fully expanded but remain deeply channelled, thus decreasing the area of exposure to the wind and increasing the rigidity of the leaf.

4. Resistance to the wind is also reduced in the tall species by the separation of all the segments to more than two-thirds their length, while in Thrinax praeceps the median segments are united more than half way up. In the latter, as in the other members of the group, the separation begins at the point of greatest width of the segment, but as if to show that the deeply divided leaves of Thrincoma are an adaptation, the greatest width is located near the longitudinal middle of the segments, 10 cm. or more above the bottom of the cleft.

5. The texture of the leaf of Thrincoma is thicker and firmer so that the segments generally remain straight to the tips while in Thrinax they often droop after the leaves have become fully expanded.

6. The color of the leaves of the tall palm is a very dark green while those of Thrinax praeceps are uniformly of a much lighter, fresher tint.

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.