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Cyperaceae

Eleocharis R.Br.

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

Common Names:

  • SPIKE-RUSH - English, United States of America
  • DOG’S-HAIR-GRASS - English, United States of America
  • SPIKE SEDGE - English, United States of America

Morphological Description

Diagnosis: Culms (= stems) green and glabrous, round, flat, or angled, with two leaf sheaths present on basal part; leaf blades absent or rudimentary; inflorescence a single terminal spikelet at the end of a usually elongate culm (hence the name SPIKE-RUSH), without bracts; scales of spikelets spirally arranged (± 2-ranked in 1 species—E. baldwinii); perianth of bristles or absent; achenes capped by a tubercle (= hardened persistent style).

Other

Notes: A cosmopolitan genus of ca. 200 species with at least 145 in the New World (González- Elizondo & Tena-Flores 2000; Smith et al. 2002). Eleocharis is a taxonomically difficult genus because it is morphologically simple, with few useful characters and because parallelism and convergence are common (González-Elizondo & Tena-Florez 2000). While the shared character of achenes with a tubercle suggests a relationship with Fimbristylis, “recent evidence [anatomy, embryology] supports a closer relationship between Scirpus and Eleocharis” (Tucker 1987). Molecular data (Roalson & Friar 2000), however, suggest a more recent common ancestry between Eleocharis and Bulbostylis. While several species grow in ponds or other standing water with a stable water level, most species grow “where receding water levels leave the plants exposed in summer” (Tucker 1987). A number of species have been reported to be significant weeds, especially in rice fields (Tucker 1987). Eleocharis dulcis (Burm. f.) Hensch. (WATER-CHESTNUT), native to the Old World tropics, has underground storage organs often used in Chinese cuisine; the juice of the tubers is also reported to have antibiotic properties (Tucker 1987). Several species vegetatively proliferate from the spikelets, particularly when growing as submerged or floating aquatics. Such plants may reproduce entirely asexually by rooting of the proliferating spikelets when the culms lean or fall and touch a substrate or water (Smith et al. 2002). Having mature achenes is extremely important for the accurate identification of the East TX species. In the descriptions presented here, the measurements given for achenes do not include the tubercles. (Greek: elos, marsh, and charis, grace; many species being marsh plants)