Description from Flora of China
Cardamine brachycarpa Franchet (1879), not Opiz (1826); C. fallax (O. E. Schulz) Nakai; C. flexuosa subsp. fallax O. E. Schulz; C. flexuosa subsp. fallax f. microphylla O. E. Schulz; C. flexuosa var. fallax (O. E. Schulz) T. Y. Cheo & R. C. Fang; C. koshiensis Koidzumi; C. manshurica (Komarov) Nakai; C. parviflora f. hispida Franchet; C. parviflora var. manshurica Komarov; C. scutata Thunberg subsp. fallax (O. E. Schulz) H. Hara.
Herbs annual, (7-)10-30(-40) cm tall, slender, glabrous or sparsely to densely pilose throughout. Stems erect, 1 to several from base, often branched above, somewhat flexuous. Basal leaves rosulate or not, often withered by anthesis; petiole 0.5-1.5 cm; leaf blade 1.5-5 cm, pinnatisect; lateral lobes 3-5 on each side of midvein, oblong, obovate, or suborbicular, sessile or petiolulate, subequaling or smaller than terminal lobe, entire or 3(-5)-toothed or -lobed. Cauline leaves including petiole (1.5-)2-6(-7) × 0.8-2.2 cm, pinnatisect or pectinate; petiole not auriculate at base; lateral lobes (2-)4-7(or 8) on each side of midvein, filiform, linear, or narrowly oblong, 3-10(-16) × 0.3-3 mm, sessile, entire or rarely 1-3-toothed; terminal lobe similar to lateral ones or slightly larger. Fruiting pedicels divaricate or ascending, 4-10 mm, slender. Sepals oblong, 1-1.5(-2) × 0.3-0.5 mm, membranous at margin and apex. Petals white, oblanceolate, (1.5-)1.8-2.5(-3) × 0.4-0.8(-1) mm. Stamens 6; filaments 1.4-2.5 mm; anthers ovate, 0.2-0.4 mm. Ovules 20-50 per ovary. Fruit linear, (0.5-)1-2(-2.5) cm × 0.6-0.9 mm; valves glabrous, torulose; style 0.3-0.7(-1) mm. Seeds pale brown, oblong-ovate, 0.6-0.9 × 0.4-0.6 mm, narrowly margined or not. Fl. May-Jun, fr. Jun-Jul. 2n = 16.
The above first records from Guangxi and Yunnan are based on Tsang 21800 (A, GH, P) and Maire s.n. (B, E, LE, W), respectively.
Cardamine parviflora has often been confused with and treated as distinct from C. flexuosa subsp. fallax. However, syntypes of the latter name, as well as the types of C. brachycarpa, C. flexuosa f. microphylla, and C. parviflora f. hispida, are morphologically the same as C. parviflora, and are therefore here reduced to synonymy.
River banks, along ditches, meadows, roadsides; near sea level to 2500 m. Anhui, Guangxi, Hebei, Heilongjiang, Jiangsu, Liaoning, Nei Mongol, Shaanxi, Shandong, Shanxi, Taiwan, Xinjiang, Zhejiang [Japan, Kazakhstan, Korea, Mongolia, Russia; N Africa, SW Asia, Europe, North America].