Eleocharis radicans |
Eleocharis obtusetrigona |
|
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creeping spikerush, radical fiber optic spikerush, root spikerush |
spikerush |
|
Habit | Plants perennial, mat-forming; rhizomes 0.2–0.5 mm thick, longer internodes 5–10 mm, scales not evident. | Plants perennial; rhizomes 3–4 mm thick, soft to hard, longer internodes 3–8 cm, scales more than 1 cm, tubers absent. |
Culms | obscurely to ca. 10-ribbed when dry, terete, 1–12 cm × 0.4–1 mm, very soft, spongy. |
obscurely 3–5-angled to terete, 40–110 cm × (2–)3.6–7.5 mm, soft, not septate-nodulose, internally spongy, transverse septa incomplete; plants never forming filiform, flaccid culms. |
Leaves | distal leaf sheaths fugaceous, colorless, translucent, apex blunt. |
distal leaf sheaths persistent, membranous, apex acute to long-acuminate, sometimes prolonged into a slender bladelike portion to 6 cm. |
Spikelets | ovoid, 2–3 × 1–1.5 mm, apex acute; scales 5–15, 5–7 per mm of rachilla, colorless to stramineous, rarely slightly reddish, medially broadly greenish to colorless, faintly 3–5-veined, often ovate, membranous, fleshy; proximal scale 2–2.5 × 0.7 mm, other scales 1.5–2 × 0.7 mm, midrib obscure to slightly keeled, apex acute to rounded. |
not proliferous, 12–43 × 3.5–6 mm; rachilla joints bearing obscure winglike remnants of floral scales; proximal scale without a flower, amplexicaulous, 3.6–7.5 mm; floral scales 30–125, 1–3 per mm of rachilla, greenish to pale brown, often with pale to dark brown submarginal band or a subapical darker spot, ovate to oblong, 4.3–5.8 × 2.5–3.3 mm, cartilaginous, often membranous toward margins, margins broadly translucent, membranous, apex rounded to acute. |
Flowers | perianth bristles equaling achene; anthers yellow to brown, 0.3–0.5 mm. |
perianth bristles 6–7, stramineous, margins and spinules reddish to pale brown, stout, flattened, subequal, exceeding achene, 2.5–3.2 mm, coarsely retrorsely spinulose; anthers reddish brown, 1.5–1.9 mm; styles 3-fid or sometimes 2-fid. |
Achenes | brownish, angles plus longitudinal ridges ca. 7, narrowly obovoid, 2 times longer than wide, 0.75–0.9 × 0.35–0.4 mm, trabeculae ca. 50, distinct. |
pale brown, biconvex, obpyriform, 1.7–2.3 × 1.2–1.5 mm, clearly sculptured at 10–15X, each face with 10–15 rows of transversely elongated cells, often isodiametric at achene base, apex usually constricted to neck 0.5–0.6 mm wide. |
Tubercles | brown, pyramidal, 0.15 × 0.15–0.2 mm. |
stramineous, lamelliform to high-pyramidal, 0.8–1.1 × 0.7–0.9 mm. |
Eleocharis radicans |
Eleocharis obtusetrigona |
|
Phenology | Fruiting spring–winter (Apr–Dec). | Fruiting spring–fall. |
Habitat | Stream alluvium, lake margins, meadows, seeps, bogs | Fresh, permanent water in ditches |
Elevation | 100–1400 Ariz., Calif., Fla., La., Mich., Okla., Tex., Va. | 0–20 m (0–100 ft) |
Distribution |
HI; n Mexico; West Indies; Central America (El Salvador); South America (Argentina, Chile)
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TX; e Mexico; South America; Central America (Nicaragua) |
Discussion | In North America Eleocharis obtusetrigona is known from only five collections, two of them originally identified as E. fistulosa (Poiret) Link [= E. acutangula (Roxburgh) Schultes], which is common in Mexico and South America. The original description of E. obtusetrigona is poor and does not clearly distinguish E. obtusangula from E. acutangula. H. K. Svenson (1939) included E. obtusetrigona in E. acutangula, which can be distinguished by its acutely trigonous culms as well as its smaller floral scales and achenes. The tubercles are often spongy as in E. quadrangulata. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 23, p. 112. | FNA vol. 23, p. 118. |
Parent taxa | Cyperaceae > Eleocharis > subg. Scirpidium | Cyperaceae > Eleocharis > subg. Limnochloa |
Sibling taxa | ||
Synonyms | Scirpus radicans, E. acicularis var. radicans, E. lindheimeri | Limnochloa obtusetrigona, E. fistulosa var. obtusetrigona, E. mutata var. obtusetrigona |
Name authority | (Poiret) Kunth: Enum. Pl. 2: 142. (1837) | (Lindley & Nees) Steudel: Syn. Pl. Glumac. 2: 80. (1855) |
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