Areca L.

Baker, W.J., Barfod, A.S., Cámara-Leret, R., Dowe, J.L., Heatubun, C.D., Petoe, P., Turner, J.H., Zona, S. & Dransfield, J. (2024) Palms of New Guinea. Royal Botanic Gardens, Kew, Richmond. 726 pp.

Morphology General Habit

Single-stemmed tree palms, crownshaft present, variously coloured, monoecious

Morphology Leaves

Leaf pinnate, straight; sheath tubular, variously coloured; petiole very short to elongate; leaflets few to numerous, rarely single-fold, usually composed of many folds, with pointed or lobed tips, arranged regularly or irregularly, horizontal-Inflorescence below the leaves, branched 2–3 orders, branches congested or widely spreading; prophyll thin, enclosing inflorescence in bud, dropping off as inflorescence expands, peduncular bract absent; peduncle shorter than inflorescence rachis; rachillae slender and usually straight

Morphology Reproductive morphology Flowers

Flowers in triads at the base of the branches, pairs or solitary male flowers towards tip, not developing in pits, female flowers much larger than the male flowers

Morphology Reproductive morphology Fruits

Fruit green ripening orange to red, stigmatic remains apical, flesh usually fibrous, endocarp thin, closely adhering to seed

Morphology Reproductive morphology Seeds

Seed 1, globose or ellipsoid, endosperm strongly ruminate.

Distribution

About 55 species from South China to India, through South-East Asia to Solomon Islands, six species in New Guinea.

Note

Areca contains understorey to mid-storey, single-stemmed tree palms. The inflorescences are presented below the leaves and female flowers occur only towards the base of the inflorescence branches. The fruiting inflorescence is club-like in the most widespread species, Areca macrocalyx. Six species occur in New Guinea, though one of these, Areca catechu (betel nut palm), is only known from cultivation. Areca is most easily confused with the closely related Pinanga, but this genus bears female flowers and fruit throughout the entire length of the inflorescence branches. The genus east of Wallace’s Line has recently been monographed by Heatubun et al. (2012a) with later additions (Heatubun et al. 2013, Heatubun 2016).

Palmae, John Dransfield. Flora of Tropical East Africa. 1994

Morphology General Habit

Minute to large, solitary or clustered, unarmed, pleonanthic, monoecious palms, almost always with a well-defined crownshaft

Morphology Leaves

Leaves reduplicately pinnate, sometimes flabellate or undivided, often with compound leaflets composed of many folds

Morphology Reproductive morphology Inflorescences

Inflorescence axillary, usually infrafoliar but occasionally interfoliar, anthesis usually occurring after leaf fall, branching to 3 orders; prophyll enclosing the inflorescence in bud, splitting and usually falling at anthesis; peduncular bracts absent; rachillae bearing basal triads of flowers, each with 1 central ♀ flower and two lateral ♂ flowers, and distal paired or solitary, 2 ranked or spiral ♂ flowers

Morphology Reproductive morphology Flowers

Male flower usually opening long before the ♀, often heavily scented, small, usually with 3 free or fused sepals and 3 free acute valvate petals; stamens 3–24 (or more); pistillode present or absent Female flower much larger than the male, with imbricate rounded sepals and petals; staminode vestiges minute or absent; ovary unilocular, tipped with 3 massive reflexed stigmas, usually with copious nectar at anthesis; ovule 1, basally attached

sex Male

Male flower usually opening long before the ♀, often heavily scented, small, usually with 3 free or fused sepals and 3 free acute valvate petals; stamens 3–24 (or more); pistillode present or absent

sex Female

Female flower much larger than the male, with imbricate rounded sepals and petals; staminode vestiges minute or absent; ovary unilocular, tipped with 3 massive reflexed stigmas, usually with copious nectar at anthesis; ovule 1, basally attached

Morphology Reproductive morphology Fruits

Fruit varying from very small to large, with stigmatic remains apical; epicarp smooth, often brightly coloured; mesocarp fibrous or fleshy; endocarp hard, somewhat woody, with longitudinal fibres

Morphology Reproductive morphology Seeds

Seed with ruminate endosperm and basal embryo

Morphology Reproductive morphology Seeds Germination

Germination adjacent-ligular; seedling leaf bifid.

General Description

Very small to moderate, solitary or clustered, acaulescent to erect, unarmed, pleonanthic, monoecious palms. Stem slender to moderate, occasionally stilt-rooted, internodes very short to elongate, leaf scars often conspicuous. Leaves undivided and pinnately ribbed, with or without an apical notch, or pinnate; sheaths forming a well-defined crownshaft with leaves neatly abscising, or rarely crownshaft not well developed when leaves marcescent or the sheaths partly open; petiole present or absent, adaxially channelled or rounded, abaxially rounded, glabrous or variously indumentose; leaflets regularly or irregularly arranged, 1–several fold, acute, acuminate or lobed, the lobes corresponding to the folds, the apical pair almost always lobed, held in one plane, very rarely (Areca insignis) with a basal auricle reflexed across the rachis, blade variously scaly or hairy, transverse veinlets obscure. Inflorescences erect or pendulous, mostly infrafoliar, rarely interfoliar in acaulescent species with marcescent leaves, in one species sometimes bursting through marcescent leaf sheaths (A. jugahpunya), branched to 3 orders basally, fewer orders distally, very rarely spicate, protandrous (or very rarely recorded as protogynous); peduncle very short to long; prophyll thin, membranous, enclosing the inflorescence in bud, quickly splitting and falling, other bracts very inconspicuous; rachis shorter or longer than the peduncle; rachillae glabrous or variously indumentose; rachilla bracts minute; triads confined to the proximal part of the main axis, or to the proximal part of each order of branching, or rarely to a subdistal part of the main axis only; rachillae otherwise bearing solitary or paired staminate flowers arranged spirally, distichously, or in 2 approximate rows on one side of the rachilla, the rachilla tips sometimes devoid of flowers. Staminate flowers frequently minute, sessile, or with a stalk formed from the receptacle; calyx with 3 distinct, slightly imbricate, triangular sepals, or cupular with 3 triangular lobes; corolla with 3 triangular, valvate petals, rarely briefly connate at the base, much longer than the sepals; stamens free or briefly epipetalous, 3, 6, 9 or up to 30 or more, filaments short to elongate, anthers linear or sinuous, sometimes very irregular, latrorse or rarely opening by apical pores; pistillode present and conspicuous as a trifid column as long as the stamens, or minute, or often absent. Pollen usually ellipsoidal, symmetric or slightly asymmetric, less frequently oblate triangular or oblate spheroidal; aperture a distal sulcus, in some species an extended sulcus, trichotomosulcus, or incomplete, presumed equatorial zonasulcus, rarely brevi or monoporate, or triporate; ectexine tectate or semi-tectate, finely to coarsely perforate, foveolate or finely reticulate, occasionally with very narrow muri, occasionally perforate-rugulate, aperture margin similar or slightly finer; infratectum columellate; longest axis 25–58 µm; post-meiotic tetrads tetrahedral, rarely tetragonal or rhomboidal [35/48]. Pistillate flowers sessile, usually much larger than the staminate, ± globular; sepals 3, distinct, imbricate; petals similar to the sepals, 3, distinct, sometimes valvate at the very tip, otherwise imbricate; staminodes 3–9 or absent; gynoecium unilocular, uniovulate, globose to ovoid, stigmas 3, fleshy, triangular, ± reflexed at anthesis, ovule anatropous or campylotropous, basally attached. Rachilla distal to pistillate flowers drying after anthesis, portions bearing fruit sometimes becoming brightly coloured. Fruit globose, ovoid, or spindle-shaped, often brightly coloured, rarely dull brown or green, stigmatic remains apical; epicarp smooth, shiny or dull, mesocarp thin to moderately thick, fleshy or fibrous, endocarp composed of robust longitudinal fibres, usually closely appressed to the seed, becoming free at the basal end or not. Seed conforming to the fruit shape or slightly hollowed at the base, with basal hilum and raphe branches anastomosing, endosperm deeply ruminate; embryo basal. Germination adjacent-ligular; eophyll bifid or rarely entire with a minute apical cleft. Cytology: 2n = 32.

Biology

Most species are small to moderate palms of the undergrowth of tropical rain forest. Areca catechu, the betel nut, is very widespread as a crop plant and seems to tolerate open conditions. Some species of Areca have very narrow ecological limits; for example, A. rheophytica is confined to the banks of fast-flowing streams on ultramafic rock in Sabah, Borneo. Areca triandra is a polymorphic species occurring from India to Borneo. Some of the entities within this complex taxon have rather precise habitat requirements.

Distribution

About 47 species, distributed from India and south China through Malesia to New Guinea and the Solomon Islands.

Morphology

Leaf, stem, root (Tomlinson 1961), root (Seubert 1998a, 1998b), gynoecium (Uhl and Moore 1971), stegmata (Killmann and Hong 1989), and fruit (Essig and Young 1979).

Vernacular

Betel nut palm, pinang, bunga, jambe.

Diagnostic

The betel-nut palm and its relatives; acaulescent, or erect, diminutive or robust palms of Southeast Asia to West Pacific, with crownshafts, with entire or lobed leaflet tips and a single large bract in the inflorescence, the pistillate flowers borne only at the rachilla bases and with basal hilum on the seed.