60. Heterolamium C. Y. Wu, Acta Phytotax. Sin. 10: 254. 1965.
异野芝麻属 yi ye zhi ma shu
Herbs erect. Leaves cordate, long petiolate. Verticillasters 2-6-flowered, pedunculate, in narrow, secund, terminal panicles; upper floral leaves bractlike, short petiolate to subsessile; bracts minute. Pedicel slender. Calyx tubular, 15-veined, pilose annulate at throat inside, limb 2-lipped; upper lip 3-toothed, middle tooth larger than lateral teeth, ovate-orbicular; lower lip with 2 narrow teeth. Corolla 2-lipped; tube exserted, without hairy annulus inside; upper lip straight, 2-lobed, lobes rounded; lower lip 3-lobed, middle lobe larger than lateral lobes, spreading, white bearded near middle outside. Stamens 4, posterior 2 much exserted between 2 lobes of upper corolla lip, anterior 2 included before pollination but much exserted after; anther cells 2, divaricate, apex confluent. Style exserted, as long as stamens, apex 2-cleft; lobes linear, slightly curved. Nutlets triquetrous, ovoid, shiny, glabrous, rounded.
Monotypic: endemic to China.
Many workers consider Heterolamium as a synonym of Orthosiphon.