Plants 30-60 cm, slender, submerged or erect. Stem simple. Leaves narrowly linear, 4-8 mm broad, encircling the stem, triquetrous at the base, rarely floating, lower part of leaf with scarious margin. Flowers in unisexual heads, borne on axes, subtended by the leafy bracts. Female heads 3-5, the lower usually pedunculate. Male heads 3- 8, remote and distinct at anthesis. Male flowers with 3 or more stamens, free or connate at the base; anthers bilobed, basifixed. 1-2 mm long; filaments c.5 mm long. Female flowers sessile or subsessile; perianth seg-ments 3 or more, 2-3 x 1-1.5 mm. spathulate, translucent with erose tips: ovary mostly sessile or shortly stipitate, usually bilocular, sometimes with one locule: style simple; stigma simple and conical. Fruits fusiform, tapering below to an obconic base with 2-4 mm long stalk (formed by shrinkage of the fruit).

Fl.Per.: July-August.

Type: U.S.S.R. Ukraine, "Im Flussbette des Row bei Bar in Podoloien", 1868, A. Rehmann 154 (Holotype: not found? BRNM or BRNU; Isotype: B,K.).

Distribution: Europe (from arctic circle to the submediterranean zone). America. Asia, China, Pakistan, Kashmir, extending eastward to Japan.

Cook & Nicholls (1986) recognized two subspecies viz. type subsp. emersum and subsp. acaule (Beeby ex Macoun) CD.K.Cook & Nicholls, and distinguished the subsp. emersum by the presence of usually remote female heads, the lower often pedunculate, lower bracts shorter or about equalling the inflorescence and the length of fruit beak shorter than the fruit body. Whereas, in the' subsp. acaule female heads crowded and usually sessile, lower bracts longer than the inflorescence and lerigth of the fruit beak equal to or larger than the fruit body. Only the type subspecies is reported from our area.

Plant is used for thatching. It is also reported to stimulate blood circulation. and eliminate blood statis in cancers of the cervix and liver as well as lymphosarcoma (Duke & Ayensu, Med.Pl.China 2: 614. 1985).