Eleocharis radicans |
Eleocharis diandra |
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creeping spikerush, radical fiber optic spikerush, root spikerush |
Wright's spikerush, Wright's spikesedge |
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Habit | Plants perennial, mat-forming; rhizomes 0.2–0.5 mm thick, longer internodes 5–10 mm, scales not evident. | |
Culms | obscurely to ca. 10-ribbed when dry, terete, 1–12 cm × 0.4–1 mm, very soft, spongy. |
often spreading or reclining, 2–25 cm × 0.3–1 mm. |
Leaves | distal leaf sheaths fugaceous, colorless, translucent, apex blunt. |
apex of distal leaf sheath acute to acuminate, tooth sometimes present, to 0.2 mm. |
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. |
ovoid, 2–7 × 1–4 mm, apex subacute; proximal scale either with flower or empty, base encircling 1/2 of culm; floral scales 50–100, 10 per mm of rachilla, orange to purple-brown, ovate, 1–1.5 × 0.8 mm, midrib slightly keeled, apex rounded to acute. |
Flowers | perianth bristles equaling achene; anthers yellow to brown, 0.3–0.5 mm. |
perianth bristles absent; stamens 2(–3); anthers yellow, 0.2–0.3 mm; styles 2-fid or some 3-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. |
0.7–1 × 0.6–0.9 mm. |
Tubercles | brown, pyramidal, 0.15 × 0.15–0.2 mm. |
deltoid 0.1–0.2 × 0.25–0.45 mm, 1/3–1/2 as high as wide, 1/8–1/4 as high and 3/4–9/10 as wide as achene. |
Eleocharis radicans |
Eleocharis diandra |
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Phenology | Fruiting spring–winter (Apr–Dec). | Fruiting late summer–fall. |
Habitat | Stream alluvium, lake margins, meadows, seeps, bogs | Fresh, mostly sandy, shores of large lakes and streams, sometimes slightly tidal |
Elevation | 100–1400 Ariz., Calif., Fla., La., Mich., Okla., Tex., Va. | 0–100 m (0–300 ft) |
Distribution |
HI; n Mexico; West Indies; Central America (El Salvador); South America (Argentina, Chile)
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CT; MA; NH; NY; VT; ON
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Discussion | Of conservation concern. Eleocharis diandra is close to E. ovata and E. aestuum; it probably should be treated as a distinct species (A. Haines 2001). It is apparently adapted to the greatly fluctuating water levels of rivers and large lakes (e.g., Oneida Lake in New York, Lake Champlain in Vermont). I have not seen specimens of E. diandra from Maine, New Jersey, or Pennsylvania, which may be based on specimens of E. aestuum. Specimens from the Lake-of-the-Woods shore in southwest Ontario are like E. diandra; they have floral scales with apices rounded, not acute as in typical E. diandra. The only recent observations of E. diandra are from the Connecticut River in Massachusetts (1985) and Oneida Lake in New York (1968; A. Haines 2001). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 23, p. 112. | FNA vol. 23, p. 103. |
Parent taxa | Cyperaceae > Eleocharis > subg. Scirpidium | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae |
Sibling taxa | ||
Synonyms | Scirpus radicans, E. acicularis var. radicans, E. lindheimeri | |
Name authority | (Poiret) Kunth: Enum. Pl. 2: 142. (1837) | C. Wright: Bull. Torrey Bot. Club 10: 101. (1883) |
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