Herbs perennial, sometimes shrubs, latex white. Rhizomes fibrous. Leaves opposite, rarely alternate, margin denticulate. Inflorescences thyrselike, terminal. Corolla campanulate or basin-shaped; throat wide, open; lobes overlapping to right. Stamens inserted at base of corolla tube, alternate with corona lobes; anthers adherent to pistil head; disc scales fleshy. Ovary half-inferior; carpels 2, free; ovules numerous in each locule. Follicles 2, slender, divaricate. Seeds numerous, apically comose; embryo straight, cotyledons as long as radicle.
"Cal deeply divided into triangular or lanceolate lobes; cor campanulate, short-cylindric, or urceolate, with short lobes, bearing within a tooth or scale near the base of the tube opposite each lobe; filaments very short; anthers lance-triangular, connate, adherent to the stigma and prolonged into a cone beyond it; ovaries 2, subtended by 5 nectaries; ovules numerous; seeds numerous, comose; colonial perennial herbs with tough fibrous bark, mostly with erect or ascending stems, opposite mucronate lvs, and small white or pink fls in terminal cymes. 3, N. Amer. Hybridization is rampant in the group. Hybrids and hybrid segregates derived from A. androsaemifolium × either A. cannabinum or A. sibiricum are called A. ×floribundum Greene (A. medium)."