Plants annual, glabrous. Stems prostrate or weakly ascending, erect when young, branched mostly from base, 0.1–0.6 m. Leaves: petiole nearly 1/2 as long as blade; blade broadly elliptic, obovate, orbiculate, or oblanceolate, (0.5–)1–3(–4.5) × 0.3–2(–2.5) cm, base cuneate, margins entire, plane to undulate, apex broadly rounded or emarginate. Inflorescences axillary clusters borne from base to apex, axes much thickened, appearing inflated, becoming indurate at maturity (only in A. scleropoides and A. crassipes). Bracts of pistillate flowers keeled (only A. scleropoides and A. crassipes have keeled bracts), deltate, 0.5–0.9 mm. Pistillate flowers: tepals (4–)5, narrowly spatulate, clawed, with small expanded blade, equal or subequal, 2–3 mm, apex rounded and apiculate; claws becoming indurate and scarious at maturity; style branches spreading; stigmas usually 2(–3), almost sessile. Staminate flowers intermixed with pistillate; tepals 5, membranaceous; stamens 3(–5). Utricles obovoid to compressed-obovoid, 1.4–2 mm, shorter than tepals, prominently muricate (especially in distal 1/2), indehiscent. Seeds dark brownish or reddish black to black, compressed-ovoid to broadly lenticular, 1–1.4 mm diam., shiny.
