Eleocharis melanocarpa |
Eleocharis obtusa |
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black-fruit spike-rush, black-fruit spikesedge |
blunt spike-rush, blunt spikesedge, broad spike spikerush, egg-shape spike-rush, éléocharide obtuse |
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Culms | to 2 times wider than thick, 35–60(–70) cm × 0.5–1.3 mm, hard, usually with to 10 blunt ribs, at 20X often finely ridged and minutely granular. |
3–50(–90) cm × 0.2–2 mm. |
Leaves | distal leaf sheaths brown to reddish. |
apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
Spikelets | 3–12 × 3–4 mm; proximal scale amplexicaulous, 3.5–4 mm, midrib region very broad and fleshy, apex entire; subproximal scale with a flower; floral scales 30–40, 8–10 per mm of rachilla, orange-brown to stramineous, midrib region stramineous, broadly ovate, papery or sometimes membranous, 3–4 × 2 mm, apex entire, rounded. |
broadly ovoid (to ellipsoid or lanceoloid), apex rounded (to acute), (2–)5–13 × (2–)3–4 mm; floral scales 15–150+, 8–20 per mm of rachilla, orange-brown (to stramineous), elliptic, 1.5–2.5 × 1–1.5 mm, midribs seldom keeled, apex broadly rounded. |
Flowers | perianth bristles present, sometimes rudimentary, brown, length variable, obscurely retrorsely spinulose; anthers brown, 1.7–2.2 mm. |
perianth bristles (5–)6–7, rarely 0, brown, stout, slightly to usually greatly exceeding tubercle; stamens usually 3; anthers brown to yellow, 0.3–0.6 mm; styles usually 3-fid and 2-fid in same spikelet. |
Achenes | subdeltoid in outline, sometimes broadly obpyriform, equilaterally trigonous, angles prominent, 0.9–1.2 × 0.7–1.1 mm, apex truncate. |
0.9–1.2(–1.3) × 0.7–0.9 mm. |
Tubercles | sessile, depressed-pyramidal, often apiculate, as wide as achene, 0.3–0.5 × 0.7–1.1 mm. |
deltoid 0.35–0.5 × (0.4–)0.5–0.8 mm, 1/3–2/3 as high as wide, 1/3–1/2 as high and 2/3–9/10 as wide as achene. |
2n | = 10. |
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Eleocharis melanocarpa |
Eleocharis obtusa |
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Phenology | Fruiting summer. | Fruiting summer–fall. |
Habitat | Fresh, oligotrophic, acid, sandy or peaty, often drying shores, ponds, ditches | Fresh shores, marshes, disturbed places |
Elevation | 10–300 m (0–1000 ft) | 10–1600 m (0–5200 ft) |
Distribution |
AL; FL; GA; IN; MA; MI; NC; NY; RI; SC; TX; VA
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AL; AR; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WY; HI; BC; NS; ON; PE; QC
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Discussion | Eleocharis melanocarpa is reported from Rhode Island; I have not seen a voucher specimen. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Extremely uncommon plants of Eleocharis obtusa without perianth bristles may be called E. obtusa var. peasei (type from New Hampshire). Robust plants with distinct caudices, floral scales 2.5 mm, and achenes 1.2–1.3 mm (Eleocharis obtusa var. gigantea Fernald) are rare (specimens seen from the Washington-British Columbia border [type], Arkansas, and the Hawaiian Islands). Dwarf plants (E. obtusa var. jejuna Fernald, type from Maine), with unusually small achenes and floral scales, and tubercles often less than 0.5 mm wide, are occasional in the East and are easily confused with E. ovata and E. aestuum. A few specimens are intermediate with E. engelmannii. Eleocharis obtusa is sometimes treated as conspecific with E. ovata, which consistently differs in its mostly 2-fid styles, mostly two stamens, and especially its narrower tubercles (B. M. H. Larson and P. M. Catling 1996). Eleocharis macounii Fernald has been treated as a synonym of E. obutsa (H. K. Svenson 1957) but is more probably a hybrid between E. intermedia and E. obtusa (P. M. Catling and S. G. Hay 1993; see 34. E. intermedia). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 89. | FNA vol. 23, p. 105. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Melanocarpae | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae |
Sibling taxa | ||
Synonyms | Scirpus obtusus, E. obtusa var. ellipsoidales, E. obtusa var. gigantea, E. obtusa var. jejuna, E. obtusa var. peasei | |
Name authority | Torrey: Ann. Lyceum Nat. Hist. New York 3: 311. (1836) | (Willdenow) Schultes: Mant. 2: 89. (1824) |
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