Eleocharis engelmannii |
Eleocharis microcarpa |
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Engelman spikerush, Engelmann's spike-rush, Engelmann's spikesedge, englemann's spike-rush |
small-fruit spikesedge, smallfruit spikerush |
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Habit | Plants usually annual, tufted, sometimes mat-forming via proliferating and arching inflorescences (stoloniferous), sometimes entirely vegetative; rhizomes absent. | |||||
Culms | 2–40 cm × 0.5–1.5(–2) mm. |
often ascending or arching, quadrangular or broadly elliptic, 2–40 cm × 0.1–0.4(–0.6) mm, soft. |
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Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent or disintegrating, pale brown, green or red-brown, streaked or mottled red-brown or purple, translucent, membranous, apex narrowly acute. |
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Spikelets | lanceoloid to subcylindric or ovoid, 5–10(–20) × 2–3(–4) mm, apex acute (to rounded); proximal scale empty, encircling ca. 2/3 of culm; floral scales 25–100(–200), 8–12 per mm of rachilla, orangebrown to stramineous, 2(–2.5) × 1–1.3 mm, midribs mostly keeled, ovate, apex narrowly rounded to subacute. |
basal spikelets absent; often proliferous, ovoid to ellipsoid or lanceoloid, terete, 2–10.7 × 1–2 mm, apex acute; proximal scale empty, persistent, amplexicaulous, dissimilar to floral scales, often longer, often resembling an involucral bract, ovate to lanceolate, midrib markedly thickened and broad and often prolonged beyond lamina; subproximal scale with flower; floral scales spiraled, colorless, whitish, or pale brown, streaked or mottled red-brown or purple, midribs green and red-brown or green and purple, ovate to elliptic, 0.8–1.5 × 0.4–0.8 mm, membranous, midrib obscure to prominent. |
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Flowers | perianth bristles present or often absent, 5–8, brown, stout, rudimentary to slightly exceeding tubercle; stamens (2–)3; anthers brown to yellow, 0.3–0.7(–1) mm; styles 2–3-fid. |
perianth bristles present or sometimes apparently absent; stamens 3; anthers 0.15–0.35; styles 3-fid. |
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Achenes | 0.9–1.1(–1.5) × 0.7–1.1 mm. |
whitish to olive or pale brown, sometimes spotted olive or red-brown, obovoid, trigonous (or subterete), angles prominent, 0.55–0.8 × 0.3–0.5 mm, apex constricted proximal to tubercle, smooth. |
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Tubercles | depressed, subdeltoid, 0.1–0.3(–0.4) × 0.6–0.9(–1) mm, 1/10–2/5 as high as wide, 1/4 or less as high as achene, 9/10 as wide as achene, very rarely 2/5 as high as achene (in E. engelmannii var. robusta). |
green or pale brown to red-brown, trigonous. |
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2n | = 10. |
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Eleocharis engelmannii |
Eleocharis microcarpa |
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Phenology | Fruiting spring–fall. | |||||
Habitat | Fresh shores, marshes, disturbed places | |||||
Elevation | 30–2400 m (100–7900 ft) | |||||
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; IA; ID; IL; IN; KS; KY; MA; MD; MI; MN; MO; MS; MT; ND; NE; NH; NJ; NM; NY; OH; OK; OR; PA; RI; TN; TX; VA; WA; WI; WV; AB; BC; MB; ON
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AL; FL; GA; IN; LA; MA; MD; MI; MS; NC; NJ; PA; SC; TN; TX; VA; West Indies
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Discussion | Robust plants known only from Missouri and described as Eleocharis engelmannii var. robusta have well-developed caudices, culms to 2 mm wide (pressed), spikelets to 2 cm, floral scales to 2.5 mm and slightly cartilaginous, styles mostly trifid, achenes to 1.5 × 1 mm, and tubercles 0.3–0.5 × 0.7–1 mm and to 2/5 as high as achene. Some specimens are intermediate between E. engelmannii and E. obtusa, or rarely with E. lanceolata. I have not seen specimens to verify literature reports of E. engelmannii from Manitoba, Connecticut, Delaware, Idaho, New Hampshire, North Carolina, Oregon, Rhode Island, South Carolina, South Dakota, or Vermont. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 2 (2 in the flora). Specimens of Eleocharis brittonii and E. microcarpa without achenes are often difficult to distinguish. More detailed study of the four apparent entities across the two species is warranted. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 23, p. 104. | FNA vol. 23, p. 95. | ||||
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | E. engelmannii var. detonsa, E. engelmannii var. monticola, E. engelmannii var. robusta, E. monticola, E. monticola var. leviseta, E. ovata var. detonsa | |||||
Name authority | Steudel: Syn. Pl. Glumac. 2: 79. (1855) | Torrey: Ann. Lyceum Nat. Hist. New York 3: 312. (1836) | ||||
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