Eleocharis interstincta |
Eleocharis wolfii |
|
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knotted spikerush |
Wolf's spike-rush |
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Habit | Plants perennial; rhizomes 2–4 mm thick, firm, longer internodes 3–7.5 cm, scales 5 mm, tubers absent. | Plants perennial, often forming large mats; rhizomes 0.25–0.6 mm thick, internodes 1–4 cm, scales 2 mm. |
Culms | 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. |
sometimes decumbent, in same plant sides variably smooth or with 1 to few acute ridges (often nearly smooth or with 1 ridge on 1 side and several ridges on the other), greatly compressed, usually inrolled when dry, rectangular in cross section, 10–40 cm × 0.3–1.5 mm, 0.2–0.5 mm thick, firm, margins often sharply acute, margins and often 1 or more ridges minutely serrulate at 20–30X. |
Leaves | distal leaf sheaths persistent, membranous to thinly papery, apex acute to acuminate. |
distal leaf sheaths persistent, red proximally, colorless or stramineous or whitish distally, slightly inflated, thickly membranous, apex acute. |
Spikelets | 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. |
ovoid or lanceoloid, 3–9 × 1.5–2.5 mm, apex acute; floral scales 15–30, 6 per mm of rachilla, orange-brown or often stramineous or colorless, midrib region stramineous or greenish, ovate-lanceolate, (2.2–)2.7–3.2 × 1.5 mm, midrib prominent, apex acute. |
Flowers | 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. |
perianth bristles absent; anthers 1.1–1.75 mm. |
Achenes | 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. |
compressed-trigonous, with angles plus longitudinal ridges ca. 9–13, prominent, obovoid, mostly 2 times longer than wide, 0.7–0.9(–1.1) × (0.4–)0.5 mm, trabeculae 30–60, rather obscure and crowded. |
Tubercles | dark brown, lamelliform, slightly higher than wide, 0.7–1.1 × 0.5–0.7 mm. |
brownish, pyramidal, usually depressed, 0.1–0.15 × 0.2–0.25 mm. |
Eleocharis interstincta |
Eleocharis wolfii |
|
Phenology | Fruiting late spring–winter. | Fruiting late spring–early summer (May–Jun). |
Habitat | Fresh ponds, lakeshores, marshes, springs, ditches, canals | Ephemeral pools in open grasslands, oak woodlands on river terraces, limestone barrens |
Elevation | 10–500 m (0–1600 ft) | 10–500 m (0–1600 ft) |
Distribution |
FL; OK; TX; Mexico; Central America; e South America
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AL; AR; CO; IA; IL; IN; KS; LA; MN; MO; MS; ND; NY; OH; OK; TN; TX; WI
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Discussion | 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.) |
Eleocharis wolfii is presumably extirpated from Colorado, Kansas, New York (Long Island), and Ohio. It was recently rediscovered in Wisconsin. Some literature reports (e.g. from the Great Plains) are based on misidentified specimens. I have not seen specimens to verify literature reports from Alberta, Saskatchewan, Colorado, Missouri, and Nebraska. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 119. | FNA vol. 23, p. 110. |
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Scirpidium |
Sibling taxa | ||
Synonyms | Scirpus interstinctus | Scirpus wolfii |
Name authority | (Vahl) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 149. (1817) | (A. Gray) A. Gray ex Britton: in H. N. Patterson, Cat. Pl. Illinois, 46. (1876) |
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