Eleocharis atropurpurea |
Eleocharis interstincta |
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purple spike-rush |
knotted spikerush |
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Habit | Plants tufted, without creeping rhizomes. | Plants perennial; rhizomes 2–4 mm thick, firm, longer internodes 3–7.5 cm, scales 5 mm, tubers absent. |
Culms | 2–12(–19) cm × 0.2–0.4 mm. |
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 firm, distally tightly sheathing, apex acute. |
distal leaf sheaths persistent, membranous to thinly papery, apex acute to acuminate. |
Spikelets | ovoid to ellipsoid, 2–6(–8) × 1–2.5 mm, apex acute; proximal scale with or without flower, not amplexicaulous; floral scales to 100, 15–19 per mm of rachilla, often loosely appressed, dark red-brown to stramineous, ovate to elliptic, 0.6–1.3 × 0.3–0.7 mm, membranous, apex rounded to acute. |
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 (0–)4–6, typically 4, colorless to whitish, vestigial to 1/2 as long as achene, smooth or spinuliferous; styles 2-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 | black, obovoid, biconvex, 0.3–0.5 × 0.3–0.4 mm, apex often constricted proximal to tubercle, smooth at 40X. |
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 | stramineous to whitish, umbonate to subconic, 0.1–0.2 × 0.1–0.2 mm, apex acute. |
dark brown, lamelliform, slightly higher than wide, 0.7–1.1 × 0.5–0.7 mm. |
2n | = 20. |
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Eleocharis atropurpurea |
Eleocharis interstincta |
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Phenology | Fruiting summer–fall (Jun–Sep). | Fruiting late spring–winter. |
Habitat | Canal banks, hammocks, irrigation ditches, lake and pond margins, maritime shores, rice fields | Fresh ponds, lakeshores, marshes, springs, ditches, canals |
Elevation | 0–1800 m (0–5900 ft) | 10–500 m (0–1600 ft) |
Distribution |
AL; CA; FL; GA; IA; KS; LA; MI; MO; NC; NE; NM; OK; SC; TX; WA; BC; Mexico; Central America; South America; West Indies; Europe (naturalized); Asia; Africa; Pacific Islands
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FL; OK; TX; Mexico; Central America; e South America
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Discussion | Eleocharis atropurpurea has been reported from Colorado, Montana, and Virginia; I have not seen voucher specimens. (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. 102. | FNA vol. 23, p. 119. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Maculosae | Cyperaceae > Eleocharis > subg. Limnochloa |
Sibling taxa | ||
Synonyms | Scirpus atropurpureus | Scirpus interstinctus |
Name authority | (Retzius) J. Presl & C. Presl: in C. B. Presl, Reliq. Haenk. 1: 196. (1828) | (Vahl) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 149. (1817) |
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