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Genus Eleocharis Family Cyperaceae

Description: Annual or perennial herbs, often rhizomatous. Culms usually tufted, erect or arcuate, terete to acutely angled.

Leaves reduced to a tubular sheath often bearing a short erect apical mucro.

Inflorescence a terminal, ebracteate, single spikelet, sometimes proliferating. Spikelet terete or angular, rarely compressed, few–many-flowered; rachilla persistent. Glumes spirally arranged, sometimes subdistichous, caducous. Flowers bisexual. Hypogynous bristles 6–10, smooth or retrorsely or rarely antrorsely scabrous or toothed, sometimes reduced, rarely absent. Stamens 1–3. Style 2- or 3-fid, usually glabrous, articulated with the nut, the dilated base persistent on the nut.

Nut trigonous or lenticular, obovoid, globose or pyriform, sometimes with a narrow neck just below the apex, crowned by the enlarged style base.


Flower
Photo Karen L Wilson

Other photo
Photo Karen L Wilson

Distribution and occurrence: World: c. 150 species, cosmopolitan. Australia: c. 30 species (10 species endemic), all States.

Some species are used for matting. E. dulcis is cultivated for its edible tubers (Chinese Water Chestnut). The record of the trop. species E. nuda C. B. Clarke from this State (NT) is apparently erroneous. Note: nut length measurements do not include the persistent style base. Treatment based on Blake (1939).

Text by K. L. Wilson
Taxon concept:

Taxa not yet included in identification key
Eleocharis parvula

 Key to the species 
1Glumes leathery, finely many-nerved with distinct midrib, not at all or only obscurely keeled, spikelet not much broader than culm2
Glumes membranous with distinct midrib, often distinctly keeled, sides nerveless; spikelet much broader than culm unless the latter is flat6
2Culms longitudinally septate internally as well as transversely septate (septa not obvious externally)3
Culms transversely septate only, obvious externally at least when dried
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4
3Culms 4- or 5-angledEleocharis philippinensis
Culms terete
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Eleocharis obicis
4Culms usually dark green, in a close linear series on a stout horizontal rhizome; in mature culms, some septa much stouter than the rest; glumes 7–11 mm long, usually with a dark red band inside the hyaline margins; nut 2–2.7 mm long; bristles 8–10Eleocharis sphacelata
Culms yellow-green, tufted (rhizome occasionally present but then slender and ascending with culms tufted along it); all septa similar in texture; glumes 5–6.5 mm long, without dark red band inside hyaline margins; nut 1.5–2 mm long; bristles 6–8
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5
5Inflorescence gradually tapering to apex; exposed portion of glumes mostly 2.5–4.5 mm long, usually longer than wide; glumes relatively long and narrow, 6–6.5 mm long, 2.5–3 mm wide, with hyaline margin 0.2–0.3 mm wide; nut c. 1.5–1.8 mm long, 1–1.5 mm diam., golden brown; bristles 6–8, united at the base, with teeth slender and irregularly retrorse; anthers 2.5–3 mm long, with apical appendage 0.1–0.2 mm longEleocharis dulcis
Inflorescence very sharply tapered to apex (almost truncate); exposed portion of glumes 1.5–2.5 mm long, usually broader than long; glumes relatively broader, 5–5.5 mm long, c. 4 mm wide, with hyaline margins 0.1–0.2 mm wide; nut c. 2 mm long, 1.5–1.9 mm diam., pale yellow-brown; bristles 6 or 7, free, slender, regularly and strongly retrorsely toothed; anthers 2–2.5 mm long, with apical appendage 0.3–0.4 mm long
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Eleocharis equisetina
6Style 3-fid, or rarely 2-fid in Eleocharis pallens and then the uppermost leaf sheath is truncate and prominently mucronate at the summit7
Style 2-fid; mouth of leaf sheath never mucronate
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19
7External surface of the nut longitudinally ridged, the intervening cells transversely linear or oblong; nut obscurely trigonous or terete; leaf sheaths membranous, with mouth oblique (often loose or difficult to observe), not dilated or thickened8
Surface of nut finely reticulate, wrinkled, pitted or smooth, the cells very small and often very faint, mostly shortly vertically oblong in very numerous series; nut trigonous or lenticular; uppermost leaf sheath thickened and differentiated at the oblique or transverse mouth
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11
8Stamens 1 or 2; bristles on nut 6 or 7, and nearly as long as nutEleocharis parodii
Stamens 3; bristles on nut few, small or absent
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9
9Nut pyriform, with c. 8 prominent ridges on each faceEleocharis macbarronii
Nut narrow-obovoid to obovoid, with 3–5 prominent ridges on each face
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10
10Spikelet ovoid, 2–7 mm long, usually setting fruit; glumes 2.0–2.5 mm long; plants neither proliferating nor with tubers; glumes dark red-brown to blackishEleocharis pusilla
Spikelet narrow-ovoid to linear, 10–20 mm long, rarely producing fruit; glumes 3–5 mm long; plants often proliferating, producing tubers; glumes red-brown
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Eleocharis atricha
11Culms clearly 4-angled, style base about as broad as nut12
Culms terete, angular-striate or flattened; style base a third to three-quarters as broad as nut
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13
12Culms to 0.5 mm diam.; spikelet 4–7 mm long; bristles 4; leaf sheath with oblique mouth, rarely minutely mucronateEleocharis pachycarpa
Culms 1–1.5 mm diam.; spikelet 10–20 mm long; bristles 6–8; leaf sheath with usually transverse mouth, mucronate
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Eleocharis tetraquetra
13Nut more or less equally trigonous with ribbed dorsal angle14
Nut biconvex or plano-convex, with the dorsal angle not ribbed if present
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15
14Nut not constricted at apex; bristles usually longer than nut; culms not obviously septate; sheaths pale brown to pale reddish, uppermost with mouth more or less oblique, sometimes mucronateEleocharis gracilis
Nut constricted to a very short neck below the apex; bristles three-quarters as long as to equalling nut; culms usually with partial transverse septa obvious when dried; leaf sheaths strongly reddish, uppermost with mouth transverse and mucronate
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Eleocharis dietrichiana
15Culms transversely septate (obvious externally at least when dried)Eleocharis blakeana
Culms not completely transversely septate
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16
16Rhizome creeping; nut not strongly ribbed on the angles; anthers with apical appendage c. 0.2 mm long; glumes tardily deciduous17
Rhizome very short; culms densely tufted; nut with prominently ribbed angles; anther appendage not exceeding 0.15 mm in length; glumes readily deciduous
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18
17Culms terete or nearly so, trigonous immediately below the spikelet (may be flattened when dried, and then mucro at mouth of leaf sheath may be in any position relative to 'margins' of 'flattened' culm); spikelet usually much broader than culm, 1.5–3 cm long, 3–7 mm diamEleocharis acuta
Culms strongly flattened when fresh even at apex; mucro at mouth of leaf sheaths always at middle of one flat face of culm; spikelet slightly broader than culm, 1–2(–4) cm long, c. 2.5 mm diam
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Eleocharis plana
18Glumes acute; spikelet more or less acute, c. 2 mm diam.; culms strongly longitudinally ridged (obvious at least when dried) with surface obviously reticulate and glistening between ridgesEleocharis pallens
Glumes rounded; spikelet more or less obtuse, 2.5–3 mm diam.; culms finely and faintly striate, dullish
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Eleocharis cylindrostachys
19Leaf sheath firm at apex; spikelet globose to ovoid; nut blackEleocharis geniculata
Leaf sheath thinly membranous, often torn at apex; spikelet ovoid or oblong-ovoid; nut pale green to dark greenish brown
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Eleocharis minuta

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