Description from Flora of China
Smithia japonica Maximowicz; S. nagasawae Hayata.
Herbs, annual, 15-60 cm tall. Stems and branchlets slender, glabrous. Stipules lanceolate, ca. 8 mm, membranous, glabrous. Leaves 10-14-foliolate; petiole 1.5-2 cm, glabrous; rachis 1.5-3 cm; petiolules less than 1 mm, glabrous; leaflet blades oblanceolate to linear-oblong, 6-12 × 2-4 mm, midvein and margin bristly, apex obtuse to rounded. Inflorescences axillary or terminal, scorpioid cymes, often with 12 or more flowers in cluster; peduncle 1-2 mm; bracts stipule-shaped, almost as long as calyx, margin ciliate. Bracteoles lanceolate, 4-5 mm, with trichomes. Calyx 4-8 mm, membranous, with reticulate veins, margin densely setose. Corolla yellow or white, slightly longer than calyx; standard obovate, ca. 5 mm wide; wings and keels small, straight, auriculate. Stamens diadelphous. Ovary with a short stipe, with trichomes. Legume a plicate loment, shortly stipitate, divided into 6-8 articles; articles almost globose, 1-1.5 mm, densely papillate. Seeds not seen. Fl. Aug-Sep, fr. Oct-Nov.
This species has been reported to have staminodes alternate with stamens (P. K. Basu, Current Science 47(3): 94. 1978).
Roadsides, mountains, wetlands; 100-2800 m. Fujian, N Guangdong, N Guangxi, SW Guizhou, Hunan, S Jiangxi, Taiwan, Yunnan, Zhejiang [Bhutan, India, Japan, Malaysia, Nepal, Philippines, Thailand, Vietnam].