Eleocharis melanocarpa |
Eleocharis obtusetrigona |
|
---|---|---|
black-fruit spike-rush, black-fruit spikesedge |
spikerush |
|
Habit | Plants perennial; rhizomes 3–4 mm thick, soft to hard, longer internodes 3–8 cm, scales more than 1 cm, tubers absent. | |
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. |
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 brown to reddish. |
distal leaf sheaths persistent, membranous, apex acute to long-acuminate, sometimes prolonged into a slender bladelike portion to 6 cm. |
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. |
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 present, sometimes rudimentary, brown, length variable, obscurely retrorsely spinulose; anthers brown, 1.7–2.2 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 | subdeltoid in outline, sometimes broadly obpyriform, equilaterally trigonous, angles prominent, 0.9–1.2 × 0.7–1.1 mm, apex truncate. |
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 | sessile, depressed-pyramidal, often apiculate, as wide as achene, 0.3–0.5 × 0.7–1.1 mm. |
stramineous, lamelliform to high-pyramidal, 0.8–1.1 × 0.7–0.9 mm. |
Eleocharis melanocarpa |
Eleocharis obtusetrigona |
|
Phenology | Fruiting summer. | Fruiting spring–fall. |
Habitat | Fresh, oligotrophic, acid, sandy or peaty, often drying shores, ponds, ditches | Fresh, permanent water in ditches |
Elevation | 10–300 m (0–1000 ft) | 0–20 m (0–100 ft) |
Distribution |
AL; FL; GA; IN; MA; MI; NC; NY; RI; SC; TX; VA
|
TX; e Mexico; South America; Central America (Nicaragua) |
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.) |
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. 89. | FNA vol. 23, p. 118. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Melanocarpae | Cyperaceae > Eleocharis > subg. Limnochloa |
Sibling taxa | ||
Synonyms | Limnochloa obtusetrigona, E. fistulosa var. obtusetrigona, E. mutata var. obtusetrigona | |
Name authority | Torrey: Ann. Lyceum Nat. Hist. New York 3: 311. (1836) | (Lindley & Nees) Steudel: Syn. Pl. Glumac. 2: 80. (1855) |
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