* * * * *
A Synopsis of the Palms of Puerto Rico.
BY O. F. COOK.
[Reprinted from the BULLETIN OF THE TORREY BOTANICAL CLUB, 28. Oct.,
1901.]
* * * * *
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.