丹草 dan cao

Hedyotis heynii (G. Don) Beddome; Oldenlandia herbacea (Linnaeus) Roxburgh; O. heynii G. Don.

Herbs, annual or biennial, generally erect, to 60 cm; stems weakly to sharply 4-angled, glabrous to scaberulous at least on angles. Leaves sessile or subsessile; blade linear or linear-lanceolate, 1-2.5 × 0.1-0.3 mm, glabrous to scaberulous, base acute to obtuse, margins weakly to strongly revolute, apex acute; secondary veins not visible; stipules reduced or fused to petiole bases, glabrous to scaberulous, truncate to broadly triangular, to 0.3 mm, entire or with 1-5 triangular to linear lobes or bristles 0.2-2 mm. Inflorescences axillary, 1-flowered or several flowered and fasciculate to cymose, glabrous, apparently ebracteate, pedunculate; peduncles 1-3 per axil, 1-30 mm; pedicels 1-30 mm. Flowers homostylous or heterostylous, subsessile to pedicellate. Calyx glabrous to puberulent; hypanthium portion subglobose to ovoid, 0.8-1 mm; limb lobed essentially to base; lobes narrowly triangular to linear, 0.5-1.5 mm. Corolla white to reddish or pale purple, funnelform, outside glabrous; tube 2-3 mm, glabrous at throat; lobes spatulate-oblong, 0.5-1 mm. Anthers exserted or included, 0.2-0.4 mm. Stigma ca. 0.8 mm, included or exserted. Fruit capsular, ovoid to subglobose, 2-2.5 × 2-2.5 mm, loculicidally dehiscent through apical beak 1-1.5 mm; seeds several, dark brown, foveolate. Fl. and fr. Jan, Mar-Apr.

On humid rocks. Fujian, Guangdong, Guangxi, Hainan, Jiangxi [widespread in tropical Africa and Asia].

Very few specimens have been seen of this species from China (or anywhere else east of Sri Lanka); the description here, therefore, is based primarily on plants from India. W. C. Ko (FRPS 71(1): 73. 1999) described the hypanthium as 1.8-2 mm, the calyx lobes as 2.5-2.8 mm and fimbriate-serrulate, the corolla lobes as ca. 2 mm, and the anthers as ca. 1.5 mm, but these features do not agree with specimens of Hedyotis herbacea; they do apply to the rather similar species H. brachypoda and H. diffusa.