鸭儿芹 ya er qin

Cryptotaenia canadensis (Linnaeus) de Candolle subsp. japonica (Hasskarl) Handel-Mazzetti; C. canadensis var. japonica (Hasskarl) Makino.

Plants 20–100 cm. Basal and lower petioles 5–20 cm, with oblong sheaths; blade triangular to broad-ovate, 2–14 × 3–7 cm; middle leaflets rhombic-obovate or cordate, 2–9 × 1.5–10 cm; lateral leaflets obliquely long-ovate to obovate, 1.5–8 × 1–6 cm. Bracts absent or 1, linear, 4–10 × 0.5–1.5 mm; rays 2–3, 0.5–3.5 cm, very unequal; bracteoles 1–3, subulate, 4–10 mm; pedicels 2–4, 1–14 mm, very unequal. Calyx teeth 0.1–0.3 mm, unequal. Petals 1–1.2 × ca. 0.6–1 mm. Fruit 4–6 × 1–1.5 mm. Fl. and fr. Feb–Oct. n = 11*.

Damp places in forests, ditches; 200–2400 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hebei, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Taiwan, Yunnan [Japan, Korea].

This species is used in traditional Chinese medicine as a tonic for strengthening the body. It is a distinctive, widespread taxon exhibiting almost continuous variation in leaf and inflorescence form across the range. It is here treated as a species (with three forms: f. japonica, f. dissecta (Y. Yabe) Hara, and f. pinnatisecta S. L. Liou) closely resembling, but distinct from, the North American Cryptotaenia canadensis (Linnaeus) de Candolle.