Description from Flora of China
Hedyotis angustifolia Chamisso & Schlechtendal; Oldenlandia angustifolia (Chamisso & Schlechtendal) Bentham; O. tenelliflora (Blume) Kuntze; Scleromitrion angustifolium (Chamisso & Schlechtendal) Bentham; S. sinense Miquel.
Herbs, annual or perennial, diffusely branched, to 40 cm tall, often drying blackened; stems subterete and smooth or weakly to sharply 4-angled and/or 2-sulcate, glabrous or often scaberulous along grooves and/or near nodes. Leaves sessile or subsessile; petiole to 1 mm, glabrescent; blade drying thinly leathery, linear, linear-lanceolate, narrowly elliptic-oblong, or narrowly spatulate, 1.2-5 × 0.15-0.4 cm, adaxially glabrous or scaberulous near margins, abaxially glabrous, both surfaces sometimes apparently scaly due to collapsed large epidermal cells, base cuneate, acute, or decurrent, margins frequently revolute, apex acute or acuminate; secondary veins not visible; stipules fused to petiole bases, triangular to rounded, 1-2 mm, puberulent, hispidulous, or glabrescent, with 2-5 linear or setiform lobes 1-4 mm. Inflorescences axillary, 1-flowered or 2- or 3-flowered in each axil, congested-cymose, glomerulate, or fasciculate, 4-8 mm in diam., sessile to subsessile; bracts acicular to lanceolate, 1-2.5 mm, entire or marginally scaberulous; pedicels to 1 mm. Flowers sessile to subsessile, apparently homostylous. Calyx glabrous; hypanthium portion subglobose to obovoid, ca. 1 mm; limb lobed nearly to base; lobes linear-lanceolate, triangular, or spatulate, 1.5-2 mm, ciliolate. Corolla white, funnelform, outside glabrous; tube ca. 2 mm, pubescent in throat; lobes narrowly spatulate-oblong, 1-2 mm. Anthers exserted, ca. 1 mm. Stigma 0.2-0.3 mm. Fruit capsular, ovoid, 2-2.5 × 1.5-2 mm, cartilaginous to stiff, loculicidal across top; seeds numerous. Fl. and fr. Apr-Dec.
This species has been treated by most authors as Hedyotis tenelliflora; however, Dutta and Deb (Taxon. Rev. Hedyotis. 2004) considered that a distinct species and treated these plants as H. angustifolia. Unfortunately, they presented no discussion of this situation nor details of the actual identity and range of "true" H. tenelliflora; consequently, their conclusion is not yet accepted here.
W. C. Ko (in FRPS 71(1): 41. 1999) described the leaves as densely rotund transparent scaly, which apparently refers to the relatively large epidermal cells that are visible under magnification and sometimes apparently collapse. This character was noted in the Fl. Bhutan (2(2): 757-764. 1999) for several Hedyotis species.
The name Scleromitrion sinense is here provisionally placed in synonymy with Hedyotis tenelliflora. As detailed by Sivarajan and Nair (Taxon 35: 363-369. 1986), the name Spermacoce stricta Linnaeus f. has also been considered by some authors to apply to H. tenelliflora (in which case it would have priority), but the identity of that Spermacoce name is so unclear and controversial, as well as involving plants from our flora area, that it is better left aside for now. Other authors have suggested that S. stricta is actually a synonym of H. verticillata.
Slopes in valleys, ridges of fields; 100-1400 m. Fujian, Guangdong, Guangxi, Hainan, Sichuan, Taiwan, Yunnan, Zhejiang [India, Indonesia, Japan, Malaysia, Philippines, Thailand, Vietnam; Australia, Melanesia].