Scandent shrubs and lianes with milky latex.
Seeds linear-compressed with an apical coma; endosperm absent.
Ovary of 2 free multiovulate carpels pubescent at apex; style glabrous, gradually dilated towards the clavuncle, contracted and then widened into the capitate stigma.
Stamens 5, sessile, inserted at about the middle of the corolla tube and with their tips reaching to the mouth of the tube; anthers conniving in a cone round the gynoecium, polliniferous in upper part only, joined to the clavuncle by a retinacle; dorsal surface of anthers often pubescent.
Corolla hypocrateriform; tube ± cylindrical, slightly wider at the middle, glabrous on outer surface except for faint alternipetalous lines of puberulence, ± glabrous within except for a circle of long stiff downwards-pointing hairs below the level of stamen-insertion; corolla lobes 5, contorted, overlapping to the right, indumentum variable.
Calyx lobes imbricate, free to base, each overlapped margin with one or a pair of delicate scales inside at the base.
Flowers borne in terminal umbellate cymes.
Leaves opposite, with a pair of triangular stipules sometimes joined into a single intrapetiolar scale, without acarodomatia or petiolar glands.
Lianas or climbing shrubs; white or clear latex in all parts (except in A. zambesiaca and occasionally A. schumannii); branches mostly lenticellate; branchlets terete, glabrous or sometimes puberulous
Inflorescence terminal, sometimes also axillary, cymose, few- or many-flowered, lax to very dense; peduncle mostly short; flowers open during the day, mostly fragrant
Leaves opposite, petiolate; ochreae often widened into intrapetiolar stipules
Corolla with variously shaped heads in mature bud more or less characteristic for the species, mostly pubescent below the insertion of the stamens and interrupted between the filament ridges; lobes overlapping to the right in bud, ciliate; tube shorter or longer than the lobes; lobes entire to sinuate-crenate, spreading or recurved
Sepals connate at the extreme base, ciliate, mostly with colleters within
Ovary of two separate carpels (united in A. multiflora), pubescent at the apex; disk absent; pistil of a basal cone or cylinder, usually with a ring at the apex and a bilobed stigmoid apex
Stamens with their tips reaching mouth of corolla tube; anthers sessile, sterile at the apex and below, pubescent below, coherent with the pistil head by a clavuncle
Fruit of two separate, thin walled, long and linear follicles (1 syncarpous in A. multiflora), dehiscent on adaxial side; seeds with a short wing at the base and a hairy coma longer than the grain attached at the apex or on a beak at the apex.