Common Trees of Puerto Rico and the Virgin Islands

nearly tliroughout the tropics, including the Old
7\Torld.
Related Species
All other native tree species of.each genus are
mentioned, usually under the first specles of the
nus or sometimes under a similar one, to aid in
Rrther identificntion. Preferred Spanish and
English names are given where known, thou 11
some species probnbl bear the same names or on y
those of the genus. !bistinyishing characters for
comparing related species with those figured hnve
been compiled lareely from Britton and Wilson
(5). Distribution 1s given by islands. In the two
lar st tree genern, Eugenia with 25 native species
an r Nicmia with 16, the other specles have merely
been listed. Keys for identification in these as
well as the other genera were published by Britton
and Wilson nlso.
Where no related species are mentioned, all nn-
tive tree species of the genus, usually only one or
two, are illustrated. However, introduced tree
species, shrubs, and herbs hnve not been cited. Of
course, some entire genern and 20 families, mostly
with few species of small, less important trees,
have been omitted.
EXPLANATION OF BOTANICAL
TERMS
Botanical descriptions for the classification and
identification on trees are based principally on dif-
ferences of leaves, flowers, and fruits, and their
parts, such as presence or absence, number, ar-
rangement, shape, size, and union or separation.
To record these details, systematic botanists, or
plant taxonomists, have a special terminolooy of
technical words derived from Lntin and creek,
defined and illustrated in botany textbooks ancl
floras. In this book, nontechnical terms have been
used wherever possible, though some technical
terms have been inserted in parenthesis or adopted
where there was no clearer equivalent. Principal
terms used in this book are explained here, while
many are illustrated by the dm\vings. Thus, it
has seemed unnecessary in include a glossnry.
Leaves
These flat, preen organs serving for food manu-
facture are very useful in the identification of trees,
us~ially present in quantities and of large size.
Tlie point. on a twig where 1 or more leave8 are nt-
taclied is the node. In arrangement on the twig,
leaves nttaclied singly or 1 at a node are altetruzte,
letives borne in pairs or 2 at a node are opposite,
and lcnves inserted 3 or more at a node are oho or led.
Parts of a lenf nre the leafsttilk or petiole and the
flat espancled part or hlrtde. In some species there
are 2 (or 1) scnles at the bnse of a leaf called
yfiptt?e.c., usually shedding early but sometimes
forming distinctive buds at the enel of n twig.
In number of blades a lenf with 1 blado is simple,
f
\vliile a compound lenf has usually several blades
(rarely only 2) called leaflets, which may or may
not have stalks. A leaflet is distinguished from a
simple leaf by the absence of a bud at the base and
by the shedd~ng of the nxis. Also, leaflets are in
2 rows long tho nxis, while simple leaves may be
si~i~ilar but more often not in 2 rows on the twig.
Compound leaves are pinnate or pinnately compound
~vlien the leaflets are inserted along a commoa
nxis and digltate (or palmate) when attached
together at the end oi the petiole. If the axis has
branches a laqf may be t~vlce pinnate or bipinnate
or if brnnclled a ain the leaf is three times pinnate
or tripinnote. %innate leaves may be even pinnate
tvllen the lenflets are aired and end in a pair, and
odd pin?lctte when en $ ing in a single leaflet.
Several terms describe the shape of leaf blades.
ri linenr leaf has a narrow grasslike blade with
arnllel, and an obloq leaf is broader but
edges with ec P ges nlso nearly parallel. A lance-shaped or
lnnceoh4e leaf hns the form of a lance, several
times longer than broad, pointed at a ex or tip
end, ancl broadest near base, while t I' le reverse
shape is oblanceolate. An mate leaf hns an oval
shape broadest to~vard the base, more or less as in
an e g, while nn obovate leaf is the reverse,
bron f est to\vard apex. An elliptic leaf has an oval
slitlpe but broadest in the center. A circular leaf
has t,he blade more or less in form of a circle, while
a spatulnte leaf is spoon-shaped.
As to margin or edge a leaf blade may be
toothed, lobed, witllout teeth, or rolled under. The
apes nnd bnse of lenf blade may be long-pointed,
short-pointed, or rounded, or the base heartshaped,
if with two rounded lobes.
In vennt ion or nrran ement of the veins a leaf
bltltle mny be paralle F -veined, if the veins are
closely placed side by side or parallel; pinnate-
(veined: with a single main vein or midrib and lateral
veins on both sides somewhnt as in a feather;
or pelmate-veined. when several main veins arise
at the base and spread like fingers in a hand.
Flower Clusters
The grouping of flowers and fruits in clusters
(inflorescences) and their location and arrangement
often provide characters useful in identification
of trees. A flower cluster is terminal when it
is at the apex or end of n twig and ZateraZ when
borne at the base of a lenf or on the side of a twig.
The flowers may be produced singly, one b one.
A npike is n flower cluster with eloncatecf axis
bearing stnlkless florr-ers, while a Taceme has an
elongated nxis with stalked flowers, and a panicle
is a compound raceme with brnnched asis. An
umbel has flowels oil spreading stalks of equal
length attached together at the npex of a larer
stalk some~vliat like an t~mbrella. A head bears
stalkless flowers on the broad disklike a ex of the
nsis. In a cyme the flower cluster is de P nite, with
the main nxis ending in the first flower and with
other flowers borne on bmnches below.