3. Equisetum fluviatile Linnaeus, Sp. Pl. 2: 1062. 1753.
溪木贼 xi mu zei
Equisetum fluviatile f. limosum (Linnaeus) Farwell; E. fluviatile var. limosum (Linnaeus) Satou; E. fluviatile f. linnaeanum (Döll) M. Broun; E. heleocharis Ehrhart; E. heleocharis f. fluviatile (Linnaeus) Ascherson & Graebner; E. heleocharis f. limosum (Linnaeus) Ascherson & Graebner; E. limosum Linnaeus; E. limosum f. linnaeanum Döll; E. limosum f. verticillatum Döll.
Plants large. Rhizome creeping or erect, castaneous, hollow in center, nodes with long castaneous adventitious roots; adventitious roots often with long yellowish trichomes. Aerial stem perennial, monomorphic, hollow in center, 40-60(-70) cm tall, 3-6 mm in diam. at middle, lower portion of main stem with 1-3 reddish brown internodes, lustrous, upper portion of main stem straw-colored or grayish green, without whorled branches or with shorter, more slender whorled branches in comparison with main stem; internodes 3-5 cm. Main stem 14-20-ridged; ridges arc-shaped abaxially and glabrous and with small light-colored cross grains; sheath tubes light brown, long, narrow, 1-1.2 cm; sheath teeth 14-20, blackish brown, lanceolate, thinly leathery, flat abaxially, without grooves, persistent. Lateral branches absent or present, if present then slender, 5-15 cm, 0.6-1 cm in diam., straw-colored or grayish green, 5-7-ridged; ridges arc-shaped abaxially and glabrous or with small cross grains; sheath teeth 4-6, straw-colored or light brown, thinly leathery, persistent. Strobilus shortly clavate or ellipsoid, 1.2-2.5 cm, 0.6-1.2 cm in diam., apex blunt; stalk prolonged when mature and 1.2-2 cm. 2n = 216.
Under bushes, river valleys, stream banks, roadsides; 500-3000 m. Chongqing, Gansu, Heilongjiang, Jilin, Nei Mongol, Sichuan, Xinjiang, Xizang [Japan, Korea, Mongolia, Russia; C and SW Asia, Europe, North America].