2. Knoxia sumatrensis (Retzius) Candolle, Prodr. 4: 569. 1830.
红芽大戟 hong ya da ji
Spermacoce sumatrensis Retzius, Observ. Bot. 4: 23. 1786; Knoxia corymbosa Willdenow; K. mollis Wight & Arnott.
Herbs or subshrubs, 20-90(-100) cm tall; roots slender, fibrous; branches terete to weakly quadrate, puberulent or villosulous to densely tomentulose. Leaves opposite, subsessile or petiolate with petiole to 12 mm, puberulent or villosulous to glabrescent; blade papery to membranous, elliptic, lanceolate, or elliptic-oblong, 3-12 × 0.8-3.5 cm, both surfaces hispid-pilosulous to villosulous or sometimes glabrescent adaxially, base acute to cuneate, apex acuminate to cuspidate; secondary veins 6-9 pairs; stipules persistent, shortly fused to petioles, deeply 3-5-lobed, 3-7 mm, villosulous to glabrescent, lobes sometimes setose. Inflorescences congested-cymose to corymbiform, sometimes trichotomous, 1-6 cm, densely strigillose to villosulous, ebracteate; peduncle 0.3-2 cm; pedicels 0.1-1 mm. Calyx puberulent or strigillose to glabrous; ovary portion ellipsoid, 0.5-0.8 mm; limb lobed essentially to base; lobes triangular, 0.1-0.3 mm, equal to subequal on an individual flower. Corolla white or purplish red, funnelform, outside glabrous; tube 1.5-2 mm; lobes triangular, ca. 1 mm. Schizocarps ovoid to ellipsoid, 2-3 mm, weakly 4-8-ribbed, strigillose or puberulent to glabrescent; mericarps coherent at dispersal; carpophore persistent, linear, ca. 2.5 mm. Fl. Jul-Aug, fr. Oct-Nov.
Thickets in open fields of low elevations. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan [India, Indonesia, Japan (Ryukyu Islands), Malaysia, Myanmar, Nepal, New Guinea, Philippines, Thailand, Vietnam; Australia].
W. C. Ko (in FRPS 71(2): 5. 1999) reported several unusual features for Knoxia mollis in China: calyx lobes ca. 1 mm, corolla bright green or rarely white, and corolla tube ca. 1 mm. These features have not been confirmed on any specimens studied for this treatment nor reported by other authors for Knoxia in SE Asia.