Robust (very rarely slender), solitary or clustered, high-climbing, spiny, hapaxanthic, dioecious, rattan palms. Stem eventually becoming bare, with long internodes and conspicuous nodal scars, sometimes bearing multiple, bulbil-like shoots in the proximal part of the lower internodes, clear gum frequently exuding from cut surfaces. Leaves of mature climbing stems usually massive, cirrate, pinnate; sheath tubular, unarmed or sparsely to very densely armed with spines, usually borne in partial whorls, and also bearing abundant, caducous, floccose hairs on and between spines; knee absent; ocrea absent; flagellum absent; petiole present or absent, it and the proximal portion of the rachis deeply channelled and sparsely to densely armed; cirrus and distal part of rachis armed abaxially with regular groups of massive reflexed grapnel spines; leaflets numerous, single-fold, entire, usually lanceolate, regularly arranged or grouped and fanned within the groups, adaxial surface often with scattered bands of caducous indumentum, the abaxial often bearing white tomentum, midribs and submarginal ribs slightly larger than other veins, transverse veinlets not evident. Inflorescences produced simultaneously in the axils of the most distal 2–20, frequently reduced, leaves, axis of inflorescence adnate to the proximal part of the internode above the subtending leaf, emerging from the leaf-sheath mouth, branching to (1) 2 (very rarely 3) orders; peduncle short; prophyll empty, tightly sheathing, 2-keeled, usually included within the leaf sheaths; peduncular bracts few, tubular, tightly sheathing; rachis much longer than the peduncle; rachis bracts similar to the peduncular, ± distichous, each subtending a pendulous first-order branch; first-order branches 3–20 or more, each with a basal tubular 2-keeled prophyll and 1–several empty tubular bracts, distal bracts very conspicuous, distichous, tubular at first, before anthesis splitting longitudinally almost to the base opposite the insertion, spreading or usually remaining imbricate and partially or completely enclosing the rachillae, or very rarely subtending second-order branches bearing similar bracts subtending the rachillae (?teratological), bract texture thin to very thick, coriaceous or subwoody, glabrous or with scattered hairs or scales; rachillae unbranched, slender, frequently densely covered in trichomes, in the pistillate inflorescence bearing from (1) 2–10 flowers, in the staminate from 2–ca. 100 flowers; staminate flowers sometimes borne in distinct dyads, otherwise basic dyad arrangement obscured by overcrowding and elongation of pedicels, rachilla bracts minute; floral bracteoles minute or obscure. Staminate flower sessile or with a stalk-like base; calyx tubular, much shorter than the corolla, with 3 short lobes; corolla tubular at the very base with 3 triangular to lanceolate lobes; stamens usually 6, rarely to 12, filaments sometimes connate basally, borne near the mouth of the corolla tube, anthers usually elongate, latrorse or introrse; pistillode minute or absent. Pollen ellipsoidal, bi-symmetric; apertures equatorially disulcate; ectexine tectate, finely or coarsely perforate (perforations sometimes sparsely distributed), perforate-rugulate, or granular-rugulate, aperture margins similar; infratectum columellate; longest axis 26–49 µm [6/16]. Pistillate flowers solitary, often pedicellate with the rachilla bract carried by adnation and subsequent growth on to the pedicel, each flower also bearing a 2-keeled bracteole; calyx tubular at the base, with 3, very short to very long, triangular lobes, usually splitting further after anthesis; corolla tubular at the base with 3, narrow to broad, triangular lobes, slightly to greatly exceeding the calyx, becoming flattened out in fruit; staminodes 6 with flattened filaments and empty anthers; gynoecium rounded, scaly, stigmas 3, usually very long, flexuous, sometimes with a well-developed style, locules 3, incomplete, ovules 3, basally attached, anatropous. Fruit 1 (rarely 2–3)-seeded, with apical stigmatic remains; epicarp covered in numerous vertical rows of reflexed scales, the scale tips frequently fringed and upward pointing, mesocarp thin, fibrous, endocarp not differentiated. Seed attached near the base, sarcotesta thick but not juicy, endosperm homogeneous; embryo basal. Germination adjacent-ligular; eophyll where known, simple, lanceolate, plicate, not split. Cytology not studied.
Clustering high-climbing pinnate-leaved rattan palms of Southeast Asia and West Malesia; sheaths lack knees and the ocrea is very short or absent; hapaxanthic and dioecious, the first-order branches of the inflorescence are pendulous and bear conspicuous dictichous bracts, partially enclosing the very short rachillae.
Plectocomia elongata and P. mulleri are the two most widespread species and also appear to have the widest altitudinal range, being found from sea level up to ca. 2000 m in the mountains; the former is characteristic of disturbed sites on poor soils and the latter is found in similar habitats but also as a conspicuous component of some facies of peat-swamp forest and heath forest (‘kerangas’). Other species are less well known and seem to be more restricted in distribution; however, many do appear to be characteristic of seral forest on poor soils. In the Himalayas, P. himalayana has been recorded at altitudes of about 2000 m. There are indications that the hapaxanthic habit may be an adaptation to the colonization of temporary habitats such as landslips. There are suggestions that, in some localities, P. elongata may flower gregariously (see Dransfield 1979a). Trigonid bees and nitidulid and staphylinid beetles have been observed visiting the intensely fragrant staminate flowers of P. dransfieldiana. Nothing is known of fruit dispersal. Neither is anything known of the time taken to reach flowering size.