Eleocharis tricostata |
Eleocharis interstincta |
|
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three-angle spikerush, three-angle spikesedge |
knotted spikerush |
|
Habit | Plants perennial, mat-forming; rhizomes evident, fairly long, 1.5–3 mm thick, hard, cortex persistent, longer internodes 1.5–3 mm, scales disintegrating to fibers, 4–5 mm, papery. | Plants perennial; rhizomes 2–4 mm thick, firm, longer internodes 3–7.5 cm, scales 5 mm, tubers absent. |
Culms | terete, often with 8–12 blunt ridges when dry, 20–55 cm × 0.3–1.3 mm, soft to hard. |
terete, 45–100 cm × (3.2–)5–9.4 mm, soft to firm, sometimes septate-nodulose proximally, not distally, internally hollow with complete transverse septa, closer together near the spikelet, evident externally; plants never forming filiform, flaccid culms. |
Leaves | distal leaf sheaths persistent, rarely splitting, proximally red to stramineous, distally green to reddish, papery, apex often dark reddish, subtruncate to obtuse, not callose, tooth present on some or all culms of plant, to 0.5 mm. |
distal leaf sheaths persistent, membranous to thinly papery, apex acute to acuminate. |
Spikelets | cylindric to ovoid, 5–20 × 2–3 mm, apex rounded to subacute; proximal scale amplexicaulous, apex entire; subproximal scale empty; floral scales appressed in fruit, 20–200+, 10 per mm of rachilla, dark brown, midrib regions often stramineous or greenish, oblong, 1.7–2.5 × 1 mm, apex entire, broadly rounded, usually recurved, mostly carinate. |
not proliferous, (20–)40–62 × 4–7 mm; rachilla joints bearing prominent wing-like remnants of floral scales; proximal scale empty, amplexicaulous, (3–)3.5–5 mm; floral scales 115–220, 1–3 per mm of rachilla, stramineous to pale brown, usually with pale to dark brown submarginal band, midrib region sometimes greenish, obovate to broadly oblong, (4–)4.5–5 × 2.8–4 mm, cartilaginous, often membranous toward margins, margins broadly translucent, membranous, apex rounded to subacute. |
Flowers | perianth bristles absent; stamens 3; anthers dark yellow, 1–1.5 mm; styles 3-fid. |
perianth bristles 6–8, stramineous, stout, flattened, subequal, exceeding achene, to 2.9 mm, coarsely spinulose; anthers stramineous to reddish, 2.5–5 mm; styles 2-fid or 3-fid. |
Achenes | falling with scales, medium to dark brown, obovoid to obpyriform, with short neck, thickly trigonous, angles prominent (keeled), 0.7–0.9 × 0.4–0.6 mm, obscurely to clearly rugulose at 10–20X with more than 20 horizontal ridges in vertical series and/or minutely cancellate at 20–30X. |
stramineous to golden-yellow or reddish brown or gray, obovoid to obpyriform, biconvex or nearly plano-convex, often with abaxial longitudinal ridge, 1.4–1.8(–2) × 1.1–1.4 mm, markedly sculptured at 10–15X, each face with 23–37 rows of transversely elongated cells, the longitudinal walls separating the cells often prominent, apex with short neck 0.7–0.8 mm wide. |
Tubercles | brown, rudimentary, mostly apiculate, sometimes pyramidal, 0.05–0.15 × 0.15–0.2 mm. |
dark brown, lamelliform, slightly higher than wide, 0.7–1.1 × 0.5–0.7 mm. |
Eleocharis tricostata |
Eleocharis interstincta |
|
Phenology | Fruiting late spring–summer. | Fruiting late spring–winter. |
Habitat | Wet sandy or peaty depressions, pond margins, pine barrens, savannas, mostly coastal plains | Fresh ponds, lakeshores, marshes, springs, ditches, canals |
Elevation | 10–200 m (0–700 ft) | 10–500 m (0–1600 ft) |
Distribution |
AL; FL; GA; MA; MI; NC; NJ; NY; SC; VA
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FL; OK; TX; Mexico; Central America; e South America
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Discussion | I have not seen specimens to verify reports of Eleocharis tricostata from Louisiana. In the absence of rhizomes and achenes, E. tricostata is easily mistaken for E. montevidensis. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Contrary to statements in the literature, sectioning reveals that the culm septa are closer together near the spikelet than in the rest of the culm in both Eleocharis interstincta and E. equisetoides. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 88. | FNA vol. 23, p. 119. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Eleocharis | Cyperaceae > Eleocharis > subg. Limnochloa |
Sibling taxa | ||
Synonyms | Scirpus interstinctus | |
Name authority | Torrey: Ann. Lyceum Nat. Hist. New York. 3: 310. (1836) | (Vahl) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 149. (1817) |
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