Stems solitary or clustered, short and subterranean, erect, or climbing. Leaves pinnate, palmate, or costapalmate, spirally or rarely distichously arranged, sometimes spiny; sheaths usually open, sometimes closed and forming crownshafts, in climbing plants usually with knees and sometimes with flagella; petioles short or absent to elongate, smooth, spiny, in palmate leaves with a hastula at apex, rarely hastula absent; rachis short to elongate, absent in palmate leaves, sometimes extended into a whiplike climbing organ (cirrus); pinnae in pinnate leaves either regularly or irregularly arranged along rachis, spreading in 1 or several planes, variously shaped, mostly reduplicate, rarely induplicate, sometimes jagged or lobed at apices, rarely gray abaxially; segments in palmate leaves variously arranged, single or multi-fold, split to varying degrees, mostly induplicate, rarely reduplicate. Plants monoecious, sometimes dioecious, iteroparous (pleonanthic) or less often semelparous (hapaxanthic). Inflorescences borne among or below leaves, solitary or rarely multiple at each node; peduncle bearing a prophyll and usually 1 or more peduncular bracts; rachis bearing prominent or much-reduced rachis bracts; rachillae 1 to many, bearing flowers in various arrangements, often solitary, paired, in threes (triads) or more; flowers usually with 3 sepals, 3 petals, 6 stamens, and 3 carpels. Fruits variously shaped and colored, sometimes covered with overlapping scales; endosperm ruminate or homogeneous; germination remote or adjacent; eophylls undivided, bifid, pinnate, or palmate.
Trees or shrubs [lianas], perennial, branched or unbranched, solitary or clustered. Roots adventitious, thick. Stems woody, subterranean or terrestrial, creeping or erect [climbing], slender or massive, sometimes conspicuously enlarged and storing starch and water, smooth or covered with fibrous or prickly remains of leaf bases. Leaves spirally arranged; sheaths tubular, often forming crownshaft, sometimes with ligular appendages; petioles terete, channeled, or ridged, unarmed or bearing prickles or marginal teeth; hastula (flap of tissue from petiole apex at junction with surface of blade) absent or present adaxially, rarely present abaxially. Leaf blade palmate, costapalmate (intermediate between palmate and pinnate), pinnate, or 2-pinnate [undivided]; plication (folding lengthwise into pleats or furrows) ^ - or tent-shaped (reduplicate, splitting along abaxial ridges) or V-shaped (induplicate, splitting along adaxial ridges); segments lanceolate, linear, or cuneate [rhombic], glabrous or variously scaly, unarmed or bearing prickles (proximal segments modified into spines in Phoenix). Inflorescences from solitary [clustered] axillary buds, borne within, below, or above crown of leaves, paniculate, rarely spicate, usually branched to 1--5 orders; prophyll (1st bract on main inflorescence axis) 2-keeled; peduncular bract(s) (empty bract[s] between 1st prophyll and 1st bract subtending branch) present [absent]; flowers bisexual, unisexual with staminate and pistillate on same plants or on different plants, or both bisexual and unisexual on same plant. Flowers solitary or variously clustered along rachillae of inflorescence, radially symmetric; perianth 1--2-seriate; sepals [2--]3[--4], distinct or connate; petals [2--]3[--4], distinct or variously connate; androecium: stamens [3--]6--34[--1000]; filaments distinct or connate or basally adnate to petals; anthers basifixed or dorsifixed, dehiscing latrorsely or introrsely; staminodes in pistillate flowers distinct or variously connate or adnate to pistil or petals; pistils 1 or 3, distinct or partially connate, each bearing 1 ovule and 1 stigma, or 1 pistil bearing 1--3 ovules and 3 stigmas; styles distinct or connate, short; stigmas dry; pistillode in staminate flower present or absent. Fruits drupaceous or berrylike; stigmatic remains basal or apical; exocarp smooth, warty, prickly, or hirsute [corky or scaly]; mesocarp fleshy or dry and fibrous; endocarp papery, leathery, or bony, sometimes with 3 germination pores. Seeds 1(--2+), free or adhering to endocarp; seed coat thin; endosperm homogeneous or ruminate, sometimes penetrated by seed coat; embryo basal, lateral, or apical, peglike, minute; eophyll (1st seedling leaf with blade) undivided and lanceolate or 2-cleft [pinnate].
Spathes various, sometimes numerous and enclosing the peduncle and branches of the inflorescence, or few, leathery or membranous; bracteoles often connate below the flowers
Stamens usually 6, in two series, rarely numerous; anthers 2-locular, loculi globose to linear, opening by slits lengthwise; pollen smooth or rarely echinulate
Ovary superior, rudimentary or absent in the male flowers, 1-3 locular, rarely 4-7 locular, or carpels 3 and distinct or connate only at the base; ovule solitary and erect or pendulous from the inner angle of each carpel or loculus of the ovary
Sepals 3, separate or connate, imbricate or open in bud
Petals 3, separate or connate, usually valvate in the male flowers and imbricate in the female
Flowers small, actinomorphic, bisexual, monoecious or dioecious, sometimes polygamous, arranged in an often paniculate inflorescence (spadix) either amongst or below the leaves
Fruit a berry or drupe, 1-2-locular, or fruiting carpels distinct; exocarp often fibrous, sometimes covered by reflexed scales
Seeds free or adherent to the endocarp; endosperm present, sometimes ruminate; embryo small
Stems stout or slender, sometimes climbing, sometimes very short or almost nothing, often covered by the persistent bases of the leaves; primary root soon disappearing and replaced by roots from the base of the stem
Leaves in a terminal cluster or in the climbing species scattered, sometimes very large, entire, pinnately or digitately divided, the segments or leaflets folded induplicately or reduplicately in bud, often sharp at the apex and prickly on the margins or midrib; rhachis often expanded at the base into a fibrous sheath
Trees to shrublets, and climbers, armed or unarmed; stems woody, very short (hence acaulescent) to immensely tall, sometimes climbing, solitary or clustered, smooth or covered with leaf-base remains or leaf-sheaths, usually prominently ringed with leaf-scars, occasionally ventricose, usually unbranched except at the base, very rarely branching aerially in a sympodial manner or by equal forking (dichotomy) or anomalously
Seed either closely adhering to the endocarp or free, sometimes with a well-developed sarcotesta; endosperm ruminate or homogeneous; embryo basal, lateral or apical
Leaves usually with a well-defined sheathing base (in some species forming a columnar pseudostem above the trunk - crownshaft); petiole sometimes very short or absent, variously armed or unarmed; lamina pinnate, bipinnate, palmate, costapalmate or simple plicate; in some climbing palms the rachis elongated into a barbed whip (cirrus), sometimes also armed with reflexed spine-like leaflets (acanthophylls); leaflets either induplicate or reduplicate, very rarely mixed, compound (composed of more than one fold) or simple (composed of single folds); in most palmate and costapalmate leaves a ligule-like structure (hastula) present adaxially at the base of the lamina, sometimes also present abaxially; leaflet margins entire or erose (praemorse), armed or unarmed
Germination remote-tubular, remote-ligular or adjacent-ligular; seedling leaves simple or compound
Plants hermaphrodite, polygamous, monoecious or dioecious, hapaxanthic or pleonanthic
Inflorescences axillary, usually single, occasionally grouped, interfoliar, infrafoliar or aggregated in a terminal mass, but here inflorescence units still axillary in axils of reduced leaves or bracts, very rarely (some Calamus spp.) some inflorescences also sterile and modified as barbed climbing organs (flagella), adnate to the internode and sheath of the leaf above; inflorescence often extremely complex with branching up to 5 orders, occasionally spicate, usually built up of a basic pattern consisting of an axis bearing a prophyll and bracts, the prophyll and 0–several of the bracts usually empty, the others each subtending a branch, in turn bearing a prophyll and bracts subtending a further order of branches and so on; ultimate branches (rachillae) bearing bracts subtending flowers, singly or in pairs, triads, or small groups, the whole flower group representing a condensed branching system (cincinnus)
Flowers hermaphrodite, male, female or sterile male (accolyte flowers of pistillate inflorescences in >i>Calamus); calyx and corolla sometimes very similar, sometimes highly differentiated, with fused or free segments, usually rather small, variously coloured (green, cream, white, yellow, rose, violet), usually but not always in whorls of 3; stamens free or united, 3–many, usually in whorls of 3, 6 or 9; anthers basi- or dorsifixed, straight or twisted; staminodes often present in pistillate flowers; gynoecium apocarpous with 1–3 (or rarely more) carpels, or syncarpous with 3 or rarely more locules, or pseudomonomerous with 1 fertile and 2 abortive locules; stigmas erect or recurved; ovule 1 only in each carpel or locule, anatropous, hemianatropous, campylotropous or orthotropous, attached basally, laterally or apically; pistillode often present in staminate flowers
Fruit usually 1-seeded, more rarely 2–10-seeded, ranging from minute to extremely large; stigmatic remains borne basally, laterally or apically; epicarp dull or brightly coloured, smooth, hairy, spiny, corky-warted or covered in reflexed imbricate scales; mesocarp fleshy, fibrous or dry, often fragrant, sometimes with copious irritant needle-crystals; endocarp well developed to absent
Dransfield, J. and N. W. Uhl. 1986. An outline of a classification of palms. Principes 30: 3--11. Henderson, A. 1986. A review of pollination studies in the Palmae. Bot. Rev. 52: 221--259. Henderson, A., G. Galeano, and R. G. Bernal. 1995. Field Guide to the Palms of the Americas. Princeton. McClintock, E. 1993. Arecaceae [Palmae]. In: J. C. Hickman, ed. 1993. The Jepson Manual. Higher Plants of California. Berkeley, Los Angeles, and London. P. 1105. Moore, H. E. Jr. 1973. The major groups of palms and their distribution. Gentes Herb. 11: 27--141. Tomlinson, P. B. 1990. The Structural Biology of Palms. Oxford. Uhl, N. W. and J. Dransfield. 1987. Genera Palmarum. Lawrence, Kans. Zona, S. 1997. The genera of Palmae (Arecaceae) in the southeastern United States. Harvard Pap. Bot. 2: 71--107.