Description from Flora of China
Asiasarum F. Maekawa; Geotaenium F. Maekawa; Heterotropa C. Morren & Decaisne; Japonasarum Nakai.
Herbs perennial; annual growth modules consisting of 2-4 cataphylls, 1 or 2 foliage leaves, and a terminal flower. Rhizomes short and vertical or long and horizontal; rhizomes and roots often pungently aromatic. Stems herbaceous. Foliage leaves solitary or paired on each growth module (when paired appearing opposite), usually long petiolate, often cordate or sagittate, margin entire. Flowers terminal, solitary (rarely paired). Perianth uniseriate, actinomorphic (rarely slightly zygomorphic). Calyx adnate to ovary to varying degrees; sepals either connate beyond attachment to ovary and forming a tube or free and forming false tube above ovary; tube cupular, urceolate, campanulate, funnelform, or cylindric, often ribbed or tessellate on adaxial surface, constricted or open at throat (orifice), throat with or without narrowly projected, contiguous shelf of tissue (orifice ring); lobes 3, erect, spreading, or reflexed. Stamens 12 in 2 series, rarely with 3 staminodes; filaments long to almost absent; anthers extrorse. Ovary inferior or half-inferior, 6-loculed; carpels fully connate. Styles 6, free or united into column, apex entire or 2-lobed; stigma terminal or lateral. Fruit a fleshy or spongy capsule, splitting irregularly when ripe. Seeds convex dorsally, plane or grooved ventrally, with fleshy funicle at base. 2n = 12, 24, 26.
No material of Asarum sprengeri Pampanini (Nuovo Giorn. Bot. Ital., n.s., 18: 113. 1911) has been seen. It is possibly related to A. chinense. The unpublished name “Asarum campaniforme” is in use among horticulturalists for a plant of apparently Chinese origin, which has large bell-shaped flowers with whitish interior of the calyx tube and almost black calyx lobes.
About 90 species: mostly in SE Asia, a few species in North America, one species endemic to Europe; 39 species (34 endemic) in China.