Large acaulescent herbs with often massive, obliquely creeping or vertically growing tubers, seasonally dying back and dormant. Leaves solitary, subtended by several basal cataphylls. Juvenile leaves entire, sagittate-hastate or ± completely divided by narrow fissures into 3 obtriangular main segments. Mature leaf with petiole erect, cylindric, not pulvinate apically, usually covered with short prickles; blade divided into 3 main segments, each segment further much divided pinnately and dichotomously into numerous lanceolate to trapezoid lobes, ultimate lobes trapezoid, apex truncate to broadly bifid with acuminate tips, decurrent; venation reticulate. Inflorescences solitary, produced before or with leaves; peduncle shorter than petiole, usually prickly (smooth in A. boehmii). Spathe longer than spadix, erect, boat-shaped, not convolute, acuminate. Spadix with pistillate basal part contiguous with apical staminate part, fertile to apex. Flowers unisexual, without perigon. Stamens subsessile; anthers lateral, dehiscing by oblique subapical slits and overtopped by thick truncate connective, or dehiscing by apical pores. Ovary unilocular, the single ovule borne on basal placenta; style shortly conic or lacking, sometimes deflexed sharply towards spadix base; stigma bilabiate and V-shaped, discoid or depressed-globose. Berries large, oblong-ellipsoid, fleshy, borne in cylindric spike, 1-seeded. Seed large, obovoid, without endosperm; testa thin.
Notes: Data on a specimen at the Kew Herbarium indicates that chimpanzees eat the berries of at least one species (A. difformis). Herbarium material lacking inflorescences is almost impossible to name with confidence at the present time. The distinguishing characters of the species lie in the inflorescence and in A. boehmii the leaf is still unknown. Further field study may yet yield useful diagnostic characters in the leaf and petiole.
HABIT : herbs, often very robust, tuber small to gigantic, erect or grossly rhizomatous, seasonally dormant. LEAF : solitary, often gigantic. PETIOLE : very long, terete, aculeate, rarely smooth, sheath very short. BLADE : sagittate when juvenile, becoming trisect at maturity, primary divisions each further divided ± dichotomously or pinnately, secondary divisions irregularly pinnatifid, ultimate lobes very variable in size and shape, distal ones larger, trapezoid, apically broader, truncate or shallowly bifid, decurrent to sessile, proximal lobes ovate and acuminate; primary lateral veins of ultimate lobes pinnate, long-arcuate, mostly running into margin, sometimes forming irregular submarginal collective vein, higher order venation reticulate. INFLORESCENCE : solitary, usually appearing before leaf. PEDUNCLE : aculeate, rarely smooth, shorter than petiole. SPATHE : erect, broadly ovate to narrowly oblong-lanceolate or oblong-elliptic, boat-shaped, not constricted, convolute basally or not at all, apex sometimes fornicate, marcescent. SPADIX : much shorter or subequal to spathe, cylindric, female zone subequal to male zone or much shorter, male zone contiguous with female, fertile to apex. FLOWERS : unisexual, perigone absent. MALE FLOWER : anthers sessile, compressed, connective slender below, thickened and dilated apically, thecae ovate-oblong, opposite, dehiscing by apical slit. POLLEN : extruded in strands, inaperturate, ellipsoid to ellipsoid-oblong, large (mean 64 µm., range 37-94 µm.), exine psilate or obscurely verruculate, very thin. FEMALE FLOWER : ovary 1-locular, ovule 1, erect, anatropous, funicle very short, placenta basal, style shortly conic or absent, sometimes strongly deflexed towards spadix base, stigma either 2-lobed and reniform to V-shaped or discoid or depressed-globose. BERRY : large, oblong-ellipsoid, fleshy, borne in cylindric spike, red, purplish or partly white. SEED : obovoid to oblong-ovoid, testa very thin, smooth, transparent, embryo large, green, endosperm absent.
Geophytic, usually robust herb with a solitary dracontioid leaf; petiole usually prickled; ultimate leaf lobes trapezoid, truncate or shallowly bifid, veins not forming regular submarginal collective vein on each side; flowers unisexual, perigone absent. Differs from Pseudohydrosme in having a long peduncle and a 1-locular ovary.