Eleocharis interstincta |
Eleocharis occulta |
|
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knotted spikerush |
limestone spike-rush |
|
Habit | Plants perennial; rhizomes 2–4 mm thick, firm, longer internodes 3–7.5 cm, scales 5 mm, tubers absent. | Plants perennial, densely cespitose; rhizomes concealed by persistent dead culm bases, often ascending, short, 3–5 mm thick, hard, cortex persistent, internodes very short, scales decaying to coarse fibers, 5–12 mm, papery. |
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. |
subterete to slightly compressed, less than 2 times wider than thick, with 4–7 blunt ridges when dry, 27–56 cm × 0.2–0.5(–0.7) mm, firm to hard, spongy. |
Leaves | distal leaf sheaths persistent, membranous to thinly papery, apex acute to acuminate. |
distal leaf sheaths persistent, not splitting, proximally red, distally green to stramineous, often inflated, thinly papery to membranous, sometimes translucent, apex broadly obtuse to subtruncate, often callose, tooth absent. |
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, 3–10 × 2–3 mm, apex acute; proximal scale amplexicaulous, apex 2-fid; subproximal scale with a flower; floral scales spreading in fruit, 20–50, 7 per mm of rachilla, medium brown, midrib region often narrowly stramineous, carinate, lanceolate-attenuate, 2–2.8 × 1 mm, apex 2-fid. |
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 3 or absent, stramineous to pale brown, rudimentary to 1/2 achene length, obscurely retrorsely spinulose; stamens 3; anthers orange-brown, 0.7–1.3 mm; styles 3-fid. |
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. |
falling with scales, medium or dark brown, obpyriform, nearly equilaterally obscurely trigonous or cross section nearly circular, 0.7–1 × 0.5–0.65 mm, neck distinct or rarely absent, obscurely rugulose at 10–30X, 30 or more low, blunt horizontal ridges in vertical series. |
Tubercles | dark brown, lamelliform, slightly higher than wide, 0.7–1.1 × 0.5–0.7 mm. |
brown, depressed-pyramidal, often rudimentary, 0.1–0.15 × 0.2 mm. |
Eleocharis interstincta |
Eleocharis occulta |
|
Phenology | Fruiting late spring–winter. | Fruiting spring (Mar–May), sometimes summer (Jul). |
Habitat | Fresh ponds, lakeshores, marshes, springs, ditches, canals | Seasonally wet, calcareous seeps, depressions, swales, rock crevises, rocky stream beds, stream banks, wet meadows, pond margins, often on limestone |
Elevation | 10–500 m (0–1600 ft) | 80–300 m (300–1000 ft) |
Distribution |
FL; OK; TX; Mexico; Central America; e South America
|
OK; TX |
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 occulta is very invariable in contrast to the extreme variability of E. compressa. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 119. | FNA vol. 23, p. 83. |
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Eleocharis |
Sibling taxa | ||
Synonyms | Scirpus interstinctus | |
Name authority | (Vahl) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 149. (1817) | S. G. Smith: Novon 11: 247, figs. 2, 3E–K. (2001) |
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