3. Hygrophila ringens (Linnaeus) R. Brown ex Sprengel, Syst. Veg. 2: 828. 1825.
水蓑衣 shui suo yi
Perennials to 80 cm tall, branched. Stems erect or decumbent at base, 4-angled, striate, slightly pubescent. Petiole 0.5-1 cm, glabrous; leaf blade narrowly lanceolate to oblanceolate, 3-10 × 0.5-1.5 cm, both surfaces with numerous cystoliths and glabrous or slightly pubescent, secondary veins 8-11 on each side of midvein, base attenuate and decurrent onto petiole, margin entire or slightly undulate, apex acute to obtuse. Flowers (solitary or)2-10 clustered in leaf axils, sessile; bracteoles narrowly ovate, 3-5 mm, margin pubescent, apex obtuse. Calyx narrowly campanulate, ca. 6 cm, 5-lobed to middle; lobes linear-lanceolate, grayish pubescent or fulvous strigose, apex acuminate. Corolla pale purple, 1-2.5 cm; tube ca. 7 mm, ca. 2 mm wide, glabrous; limb 2-liped; lower lip obovate, ca. 3 mm, 3-lobed to middle, lobes ovate with an obtuse apex; upper lip elliptic, ca. 3 mm, shallowly 2-lobed, outside puberulent. Stamens 4, included; filaments glabrous, longer pair ca. 5 mm, shorter pair ca. 3 mm; anther thecae 1-2 mm. Ovary glabrous; style filiform, ca. 8 mm, included; stigma unequally 2-lobed. Capsule narrowly oblong, 0.8-2.2 cm, ca. 1.5 mm wide, glabrous, 12-18-seeded. Seeds ca. 1 mm, pubescent. Fl. Aug-Oct, fr. Dec-Feb.
Along streams, wet places; below 1000 m. Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [Bhutan, Cambodia, India, Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Thailand, Vietnam].