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Cyperaceae

Rhynchospora Vahl

Kingdom: Plantae Rank: Genus Parent: Cyperaceae Status: Valid

Common Names:

  • BEAK-RUSH - English, United States of America
  • HORNED-RUSH - English, United States of America
  • BEAK SEDGE - English, United States of America
  • WHITE-TOP - English, United States of America

Morphological Description

Diagnosis: Tufted or clump-forming, sometimes rhizomatous perennials (rarely annuals), glabrous or with scabrous-margined leaf blades; culms (= stems) triangular in cross section; leaves basal and cauline; spikelets narrowly ovoid to fusiform or roundish, usually brownish or white (in a few species) or dark brown to nearly black (in a few species), usually 1–few-flowered, in loose or compact clusters, in spike-like or open panicles, or in a head-like cluster, the inflorescence with 1–few leafy bracts; scales of spikelets spirally arranged, the lower (1–)2–3 usually sterile; uppermost 1–2 florets usually without pistil; perianth of bristles or absent; achenes flattened to lenticular to nearly round in cross section, with a conspicuous tubercle or “beak” (= hardened and persistent style base) at the apex (hence the name BEAK-RUSH).

Other

Notes: A genus of over 250 species nearly cosmopolitan in distribution, with greatest diversity in the New World tropics; they are mostly plants of sunny places with wet, acidic soils (Kral 2002c). Temperate North America is rich in species, with ca. 60 in the se U.S. (Tucker 1987). According to Yatskievych (1999), species of this genus “are generally considered poor forage for livestock. The tiny sharp teeth along the leaf margins are composed of silica, and they make the plants relatively unfit for consumption.” However, many marshland species provide food for migratory waterfowl (Kral 2002c). In the key and descriptions presented here, the measurements given for achenes do not include the tubercles. (Greek: rhyncos, a snout, and spora, a seed, from the beaked achenes)