5. Polygonum cognatum Meisner, Monogr. Polyg. 91. 1826.
岩萹蓄 yan bian xu
Polygonum myriophyllum H. Gross; P. rupestre Karelin & Kirilov.
Herbs perennial. Root ligneous, stout, ca. 1.5 cm in diam. Stems prostrate, 8-15 cm, branched from base, angulate, minutely papillate along angles. Petiole 2-5 mm, base articulate; leaf blade elliptic, 1-2 cm × 5-13 mm, both surfaces glabrous, abaxially with prominent midvein, adaxially with conspicuous midvein; ocrea silvery, thinly membranous, hyaline, veined, apex lacerate. Flowers 1-5, in axillary fascicles; bracts ca. as long as lower leaves, membranous, apex acuminate. Pedicel 1-3 mm. Perianth green, margin pinkish or white, 5-cleft to 1/2; tepals ovate, 1.5-2 mm, becoming hard in fruit. Stamens 8, included; filaments dilated at base. Styles 3; stigmas capitate. Achenes included in persistent perianth, black, shiny, ovoid, trigonous, 2.5-3 mm. Fl. Jun-Aug, fr. Jul-Sep.
Gravelly mountain slopes, dry riverbeds; 1400-4600 m. Nei Mongol, Xinjiang [Kazakhstan, Kyrgzystan, Mongolia, Russia (Siberia), Tajikistan].