HABIT : seasonally dormant (sometimes irregularly so) or rarely semi-evergreen herbs, often large, sometimes gigantic, tuber usually depressed-globose, sometimes irregularly ± elongate-cylindric, napiform or carrot-shaped, rarely rhizomatous or stoloniferous. LEAVES : usually solitary (rarely 2-3) in adult plants, sometimes 2-3 in seedlings. PETIOLE : long, usually smooth, rarely verrucose to asperate, sometimes very thick, usually conspicuously spotted and marked in a variety of patterns, sheath very short. BLADE : trisect, primary divisions pinnatisect, bipinnatisect or dichotomously further divided, tubercles rarely present at junction of divisions, secondary and tertiary divisions ± regularly pinnatifid to pinnatisect, ultimate lobes oblong-elliptic to linear, acuminate, decurrent, rarely petiolulate; primary lateral veins of ultimate lobes pinnate, forming distinct submarginal collective vein, higher order venation reticulate. INFLORESCENCE : always solitary, preceded by cataphylls, usually flowering without leaves, rarely with the leaves. PEDUNCLE : very short to long, similar to petiole. SPATHE : variously coloured, marcescent and finally deciduous, boat-shaped and not or hardly convolute, or clearly differentiated into tube and blade, sometimes constricted between them; tube convolute, rarely connate (A. pusillus, A. elliotii), campanulate to cylindric or ventricose, inner surface smooth, longitudinally ribbed, near base verruculose, scabrate or densely covered with scale- or hair-like processes or smooth; blade erect to spreading, smooth, ribbed or variously undulate or frilled at margins. SPADIX : shorter or much longer than spathe; female zone shorter, equalling or longer than male zone; male zone cylindric, ellipsoid, conoid or obconoid, usually contiguous with female, sometimes separated by a sterile zone which may be naked, or bear prismatic, subglobose or hair-like sterile flowers; terminal appendix usually present, rarely absent or reduced to stub, erect, sometimes horizontal, rarely pendent, very variable in shape, usually ± conoid or cylindric, rarely ± globose, sometimes ± stipitate or basally narrowed, usually smooth or bearing staminode-like structures near base or entirely covered with staminodes, sometimes corrugate or densely to sparsely hirsute, or grossly and irregularly crumpled. FLOWERS : unisexual, perigone absent. MALE FLOWER : 1-6-androus, stamens free or sometimes connate in basal flowers or throughout male zone, short, filaments absent or distinct, connective fairly thick, sometimes projecting beyond thecae, thecae obovoid or oblong, opposite, dehiscing apically by an apical (rarely lateral) pore or transverse slit. POLLEN : extruded in strands, inaperturate, mostly ellipsoid to ellipsoid-oblong, occasionally spherical or subsphaeroidal, medium-sized to large (mean 53 µm., range 34-82 µm.), exine striate, striate-reticulate, psilate, punctate-foveolate, verrucate, or spinose. FEMALE FLOWER : gynoecia usually crowded, sometimes ± distant, ovary subglobose to ovoid or obovoid, 1-4-locular, ovules 1 per locule, anatropous, funicle very short to distinct, erect, placenta axile to basal, style absent, short or very long, conoid to cylindric, stigma variably shaped, entire and subglobose or 2-4-lobed, stellate or rarely punctiform, sometimes large and brightly coloured. BERRY : sometimes very large, 1 to few-seeded, orange to red, rarely blue or white, infructescence ± cylindric. SEED : ellipsoid, testa smooth, thin, embryo large, somewhat green superficially, endosperm absent.