Perennial herbs, with erect leafy stems from extensive rhizome-systems. Leaves alternate, with long sheathing bases forming a pseudostem; sheaths sulcate or reticulate; ligule present; base of lamina contracted into a pseudopetiole; laminas of lowest leaves reduced, upper laminas ovate to obovate, usually glabrous above, variously pubescent beneath or glabrous; lateral nerves easily visible beneath but sometimes obscured by hypodermal sclerenchyma above. Inflorescences terminating separate leafless shoots arising either at the base of the leafy shoots, or from the rhizomes, or from both of these positions; peduncle with distichous bracts; flowers clustered at the apex of the peduncle (but axis elongated in A. laxiflorum), each subtended by 2 subopposite bracts. Flowers large, strongly zygomorphic. Calyx spathaceous, splitting unilaterally at anthesis. Lateral petals narrow, often recurved; posterior petal larger, usually oblong and concave, forming a hood-like structure. The basal half of the petals and the androecium are fused into a tube. Androecium consisting of 1 broad petaloid staminode (the labellum) and a single free stamen, with subulate outgrowths of doubtful homology usually present on each side of the stamen-base; free filament ligulate, the apex 3-lobed except in A. laxiflorum and A. zambesiacum; anther-thecae 2, subterminal. Labellum either broad, very delicate, and suberect, or narrower, thicker and decurved. Ovary inferior, 3-locular; style filiform, passing between the anther-thecae and ending in a trumpet-shaped stigma with a ciliate margin. Subulate or contorted nectaries (“stylodia”) are found at the base of the style. Fruit a large indehiscent berry with a tough fleshy wall, usually red when ripe, with an apical beak formed from the persistent calyx, the style-base, or a sterile prolongation of the ovary. Seeds hard, black or brown, surrounded by white translucent arils, cohering into 3 masses around the delicate axile placenta.
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