2. Equisetum palustre Linnaeus, Sp. Pl. 2: 1061. 1753.
犬问荆 quan wen jing
Equisetum palustre f. polystachion (Weigel) Villars; E. palustre var. polystachion Weigel; E. palustre var. szechuanense C. N. Page.
Plants small to medium-sized. Rhizome erect or creeping, blackish brown, nodes and roots with long yellowish brown trichomes or glabrous. Aerial stem annual, monomorphic, with branches often clumped at base of aerial stems, 20-50(-60) cm tall, 1.5-2 mm in diam. at middle, green, but those of lower 1 or 2 nodes blackish brown, not lustrous; internodes 2-4 cm. Main stem 4-7-ridged; ridges arc-shaped abaxially and glabrous or with small cross grains; sheath tubes long, narrow, lower portion grayish green, upper portion light brown; back of sheath with a shallow groove; sheath teeth 4-7, blackish brown, lanceolate, membranous at margin, acuminate at apex, persistent. Lateral branches robust, up to 20 cm, terete to complanate, 4-6-ridged, glabrous or with small pale cross grains; sheath teeth 4-6, grayish green, lanceolate, thinly leathery, persistent. Strobilus ellipsoid or terete, 0.6-2.5 cm, 4-6 mm in diam., apex blunt; stalk prolonged when mature, 0.8-1.2 cm. 2n = 216.
Under bushes, roadsides; 200-4000 m. Chongqing, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Japan, Kashmir, Korea, Mongolia, N Pakistan, Russia; C and SW Asia, Europe, North America].