HABIT : seasonally dormant herbs, tuber hypogeal, subglobose or rhizomatous and horizontal. LEAVES : 3-4(-6) in each sympodial unit. PETIOLE : sheath long to short. BLADE : cordate (A. pictum) or hastate-sagittate to sagittate; primary lateral veins pinnate, forming submarginal collective vein, at least 1 marginal vein also present, higher order venation reticulate. INFLORESCENCE : 1, rarely 2 in each floral sympodium, usually appearing with leaves, rarely just before (A. pictum), hidden within foliage or fully exposed above leaves. PEDUNCLE : much shorter to much longer than petiole. SPATHE : marcescent, usually strongly constricted between tube and blade, rarely not, tube convolute, cylindric to ellipsoid, blade ovate- or oblong-lanceolate to lanceolate, ± acuminate, at anthesis erect and boat-shaped or widely expanded or patent and ± revolute. SPADIX : shorter to longer than spathe, sessile, female zone cylindric, interstice separating male and female zones usually short, rarely absent, usually covered with sterile flowers (pistillodes), rarely naked, male zone cylindric, conoid, ellipsoid or subglobose, interstice separating appendix and male zone usually covered with sterile flowers (staminodes), rarely absent, terminal sterile appendix usually stipitate, then gradually or suddenly dilated into a conoid or cylindric club, sometimes slender. FLOWERS : unisexual, perigone absent. MALE FLOWER : 3-4-androus, filaments very short but distinct, connective slender, thecae shortly obovoid, opposite or subopposite, dehiscing by apical pore-like slit, rarely porose (A. pictum). POLLEN : usually presented in a loose, powdery mass, sometimes extruded in strands (A. pictum, A.nigrum), grains inaperturate, spherical to subspheroidal, medium-sized (mean 32 µm., range 29-34 µm.), exine spinose, rarely scabrous (A. korolkowii). STERILE FLOWERS : (staminodes and pistillodes) consisting of basal, ± hemispheric, swollen, verrucose to smooth portion bearing usually one (sometimes more) erect, ± straight, subulate to filiform processes. FEMALE FLOWER : gynoecium oblong, obtuse, ovary 1-locular, ovules 6-more, orthotropous, lageniform, biseriate, funicle short, placenta parietal to subbasal, style short, as broad as ovary, stigma subhemispheric, exuding nectar drop at anthesis. BERRY : obovoid, pericarp juicy, many-seeded, bright glossy orange-red. SEED : ellipsoid to ovoid, testa rugose, especially towards base, with large, succulent obconic strophiole, embryo axile, straight, endosperm copious.
Seasonally dormant, rhizomatous or tuberous geophytes. Leaf blade sagittate or hastate, with reticulate venation. Spadix usually with zone of sterile flowers between male and female zones, more rarely with fertile zones contiguous or with naked axis between zones; spadix with smooth terminal sterile appendix. Placentation parietal to subbasal.