Chapter I: Part 1

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A Synopsis of the Palms of Puerto Rico.

BY O. F. COOK.

[Reprinted from the BULLETIN OF THE TORREY BOTANICAL CLUB, 28. Oct.,
1901.]

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A Synopsis of the Palms of Puerto Rico

BY O. F. COOK

(WITH PLATES 43–48)

The following systematic notes have been accumulated in connection with economic studies of Puerto Rico[1] palms, and although the list is doubtless still incomplete, the printing of it may be justified as a means of securing at least provisional names needed for reference purposes in connection with other publications of a non-systematic character.

The palms may well be considered a very refractory group when handled by the conventional methods of systematic botany. Difficult at once to collect or to study from dried material, they are commonly neglected both in the field and in the herbarium, with the result that literature is scanty and unsatisfactory. A very large proportion of the descriptions are entirely inadequate for the identification of species, and there has been much lawlessness and diversity in the application of generic names, as will appear from some of the instances discussed below. Difficulties of description and classification have also been multiplied by the fact that the palms are such peculiar plants that analogies and criteria borrowed from other families are often inapplicable and misleading. Moreover, the terminology of parts and characters has not been developed to the point where the expression of observed differences is easy, and available language often fails completely to suggest the significance of the characters used. Thus the fibers into which parts of the leaf-bases of many palms are resolved afford many diagnostic characters, for which we have no parallels in other groups of plants.

A compensating advantage may be drawn, however, from the definite and often very limited geographical distribution of the species of palms. Thus, although Puerto Rico is a relatively small island, several of the indigenous palms have apparently ranged in nature over but a small part of it, and a locality definitely indicated would often go further toward establishing the identity of a species than much of the descriptive matter prepared for this purpose. For the present, at least, the geographical idea should be kept uppermost in systematic studies of the palms, since it is generally much easier and far more logical to extend the limits of supposed distribution and unite supposed species, than to cope with the confusion caused by the miscellaneous reporting of species far outside their natural ranges.

From the popular standpoint another serious inconvenience of the systematic literature of palms arises from the fact that it is based so largely on floral characters that even the botanical traveler might need to wait months for the blossoms and then climb the trees or cut them down before being able to secure a clue to botanical names or relationships. But however necessary refinements of formal characters may be in presenting classifications or monographs of large groups, more obvious differences may still be adequate for distinguishing between the species, genera and families represented in a limited flora like that of Puerto Rico. In the present paper use is made therefore of obvious external differences, not only because of the greater convenience and utility of such facts in field study but also in the belief that with the palms, at least, the vegetative, habitat and ecological features are often quite as important for diagnostic purposes as the more technical and conventionalized characters to which botanists are accustomed in dealing with other natural orders.

As will be apparent from some of the following systematic notes, the generic nomenclature of the palms is in a condition closely comparable to that now known to obtain among the myxomycetes, fungi, hepaticae and ferns. Possibly the palms have suffered more from neglect and carelessness than other groups of flowering plants, but it can no longer be maintained that the practical defects of former taxonomic methods do not exist in the phanerogams as well as in the cryptogams, and it becomes obvious that the enactment of different nomenclatorial legislation for these two subdivisions of the vegetable kingdom would be unreasonable and inconsistent.

The present list records twenty palms from Puerto Rico, of which three are introduced and seventeen are supposed to be native species. As may also be inferred from many other groups of plants Puerto Rico appears to be a rather remote corner of the Antillean region, which many types present in Cuba and Jamaica did not reach, whether by reason of greater distance from the continent or because of an earlier interruption of land communication. The native palms of Puerto Rico may thus be said to represent a distinctly Antillean or Caribbean series, only _Acrocomia_ and _Bactris_ being known to have a wider distribution.

The list of introduced palms, consisting of the date, the cocoanut, and the betel, might have been somewhat increased by canvassing ornamental gardens, but it does not appear that any other introduced species has been put to any useful purpose or has escaped into general culture, certainly a remarkable fact when we consider the number and importance of the economic palms of other tropical countries.

Finally, it may be well to note here that several palms have been reported from Puerto Rico which probably do not exist in the island; at least their occurrence is not supported by adequate evidence. Thus Mr. R. T. Hill, of the United States Geological Survey, mentions (Bull. U. S. Dept. Agric., Division of Forestry, 25: 1899) as occurring in Puerto Rico seven palms, as follows: _Cocos Mauritia_, _Oreodoxa oleracea_, _Cocos nucifera_, _Martinezia caryotaefolia_, _Mauritia flexuosa_, _Oreodoxa regia_, and _Caryota_ sp., of which list only _Cocos nucifera_ and _Oreodoxa regia_ appear to have been justified.

The reference to _Oreodoxa oleracea_ is supported by the botanical authority of Professor Drude, but the specimens identified by him as _Oreodoxa oleracea_ (Sintenis collection, no. 1525) and sent from the Berlin Botanical Garden to the National Herbarium and to the New York Botanical Garden are not _Oreodoxa oleracea_, but belong to the new genus _Acrista_ described below, while a specimen collected by Sintenis (no. 5749) at Aguadilla and sent out from Berlin as an _Attalea_ or related genus is not even a cocoid palm but _Areca catechu_, the betel nut of the Malay region.

The existence of numerous tubercles on the roots of a young specimen of the royal palm of Puerto Rico is a fact of biological interest and possible economic importance. It was, however, noted so nearly at the end of our last visit that further studies were not practicable, but barring possible nematodes or other pathological causes for the tubercles it appears that we must add palms to the Leguminosae, _Podocarpus_, _Alnus_, and _Cycas_ as plants which have, as it were, domesticated nitrogen-collecting soil organisms.

The field notes, specimens and a considerable series of illustrations for publications of the Department of Agriculture were secured during two visits to Puerto Rico, the first in November and December, 1899, the second in June and July, 1901. The photographs are the work of Mr. G. N. Collins.

Key to the Families

Leaves fan-shaped; branches of inflorescence subtended by spathes.

Family SABALACEAE, p. 529.

Leaves feather-shaped; spathes few, not subtending the branches of the
inflorescence.

Leaf-divisions v-shaped in section, concave above; trunk rough
with leaf-bases or prominent diamond shaped scars.

Family PHOENICACEAE, p. 528.

Leaf-divisions inverted v-shaped in section, convex above; trunk
smooth or the leaf-scars ring-like and not prominent.

Leaf-bases long-sheathing, green and fleshy, finally split down
the side opposite the midrib permitting the leaf to fall;
fruits with fleshy, fibrous or woody endocarps.

Family ARECACEAE, p. 546.

Leaf-bases sheathing only while young, with maturity separating,
except at the midrib, into a dry fibrous network which must
tear or decay before the leaves fall; fruits with a stony
endocarp perforated by three foramina.

Family COCACEAE, p. 558.

Family PHOENICACEAE

This family contains a single genus of old-world palms usually associated with the fan-leaved series, and differing from all other feather-palms by having the concave side of the leaf segments turned upward.

PHOENIX DACTYLIFERA Linn. Sp. Pl. 1188. 1753

The date palm was probably introduced into Puerto Rico in the early part of the Spanish occupation of the island, and isolated trees are to be found in many localities especially in the vicinity of the larger towns. The climate is, however, too cool and too moist to permit the fruit to ripen properly, and there is apparently no inducement for planting in large quantities.

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.

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.

Spathe single, the fruits 2.5 cm. long; leaf-divisions upright,
very dark green.

ARECA.

Spathes 2, fruits less than 1.25 cm. long; leaf-divisions
horizontal or oblique.

Trunk robust, thickened near the middle; leaf-divisions
inserted by twos and standing at different angles;
inflorescence twice or thrice branched, standing close
to the leaf-bases.

ROYSTONEA.

Trunk slender, of uniform diameter; leaf-divisions at
equal distances, horizontal; inflorescence
once-branched, at maturity 15 cm. or more below the
leaf-bases.

ACRISTA.

=Aeria= gen. nov.

A tall slender palm evidently related to _Gaussia_, but the embryo lateral instead of basal, and the pinnae without basal cushions.

Among palms in Puerto Rico _Aeria_ resembles only _Acrista_, from which it is readily distinguishable by the very slender habit, the swollen base of the trunk, the much-branched slender interfoliar inflorescence, the shorter sheathing bases of the leaves, and the numerous spathes.

The embryo of _Aeria_ is located near the longitudinal middle of the seed on the side opposite the rudiment of the style, which is here located at the base of the fruit instead of on the side as in _Acrista_. The albumen is also uniform, except for a small central cavity and the outer covering is fleshy rather than fibrous.

The position of the embryo is, perhaps, the most obvious difference between this genus and _Gaussia_, but there are several other significant discrepancies. Thus the flowers are arranged 3 or 4 in a row, very seldom 5 or 6. Three fruits develop from one flower only exceptionally. The trunk is of more than medium height, and the inflorescence is in reality infrafoliar, for although the dead leaf-bases and midribs of the leaves are persistent and support the long inflorescence, this condition is not comparable to that of the cocoid and other really interfoliar inflorescences.

=Aeria attenuata= sp. nov. Plate 45.

The tallest of Puerto Rico palms, probably attaining 30 metres and upward. The trunk is supported on a mass of coarse roots with spine-like projecting rootlets arranged in whorls. The surface of the trunk is smooth with very faint annular impressions. Near the ground the diameter is 12 to 15 cm. and increases upward to about 25 cm. at about 3 m. above the base. Above this swelling the trunk tapers very gradually and in tall specimens is less than 7 cm. in diameter at the top.

The sheathing leaf-base is only 20 cm. long. The leaves remain attached long after the rupture of the open side, but no fibers are formed, the edges of the split side being fringed only with brown membranous shreds. The petiole is rather short, round and rigid and the rachis is prominently angled above.

Segments of a rather firm texture and standing in different planes, but all more or less upright or oblique to the rachis, segments from middle of leaf 2.3 cm. wide near the base, 3.8 cm. long. The segments are set very closely together, especially the proximal, and overlap each other in a succubous manner. Fresh fruits deep orange in color and of an unsymmetrical oval in shape, 16 mm. by 12 mm., with a firm, fleshy outer covering 1.6 mm. thick, adherent to the seed, the three persistent styles remain of the same size and are located at the base of the fruit.

The seed is flattened oval, 11 mm. by 9 mm., with a prominent basal tubercle (hilum). The surface is brownish with a few shallow impressed lines, but the albumen is white and uniform. Flowers and ripe fruit were obtained at Vega Baja in December, 1899; type specimen no. 1040.

The so-called llume palm is a most striking ornament of the rugged limestone hills from Vega Baja to Manati and Arecibo. At a sufficient distance the slender trunk is no longer visible and the crown of leaves appears as if suspended in mid-air, while at closer range it does not seem possible that so slender a shaft can maintain itself. This very slenderness with the attending flexibility is however, an element of strength since it permits the trees to bend before the wind while the leaves diminish the resistance by straightening out as in the cocoanut. The hurricane of August, 1899, seemed to have done little damage to these tallest of Puerto Rico palms, many of which project for more than half their height above everything standing about them. As the trees of the rather sparse forest growth of these hills are commonly from 12 to 18 metres tall, the llume palms must often attain upwards of 30 metres.

ARECA CATECHU Linn. Sp. Pl. 1189. 1753