Trichosclereids sparsely present in vegetative parts (Seubert, pers. comm.), more abundant in style (Carvell 1989). HABIT : evergreen herbs, often very robust, stem climbing or prostrate, usually producing long flagellae with reduced cataphylls. LEAVES : many, often remote from one another. PETIOLE : geniculate apically, sheath usually less than half as long as petiole. BLADE : ovate-cordate or pandurate-trilobed or pinnatisect, sometimes with ± numerous round to oval perforations near midrib; primary lateral veins pinnate, running into marginal vein, higher order venation reticulate. INFLORESCENCE : 1-several in each floral sympodium. PEDUNCLE : erect, subequal or half as long as petiole. SPATHE : conchiform to ovate, apiculate, sometimes reflexed at anthesis and then deciduous. SPADIX : sessile to long-stipitate, sometimes very short. FLOWERS : bisexual, perigone absent. STAMENS : 4, filaments short, broadly linear, anthers equalling or shorter than filaments, thecae ovoid, extrorse, dehiscing by longitudinal slit. POLLEN : fully zonate, hamburger-shaped, medium-sized (mean 39 µm., range 38-41 µm.), exine either densely and minutely punctate in one half and virtually psilate in other, or uniformly foveolate-fossulate, apertural exine psilate or obscurely verrucate. GYNOECIUM : obpyramidal or obconoid, tetragonal, ovary 1-locular, ovules 2, anatropous, funicle short, placenta near base of deeply intrusive septum, style broader than ovary, slightly prominent centrally below stigma, otherwise ± truncate, stigma small, hemispheric. BERRY : subglobose, truncate to domed at apex, white (A. medium, A. humile) or orange-red (A. magnificum, A. zippelianum) when ripe. SEED : subglobose to heart-shaped, testa smooth, glossy, embryo curved and partly green, endosperm present (E. Seubert 1993).
Climbing hemiepiphytes on tree trunks or creeping on forest floor; trichosclereids only sparsely present in vegetative parts; higher order leaf venation completely reticulate; flowers bisexual, ovary 1-locular, placenta 1, intrusive parietal, ovules 2; seeds subglobose to heart-shaped. Notable among Monsteroid genera for the combination of reticulate fine venation and absence of perigone.