Eleocharis microcarpa |
Eleocharis brittonii |
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small-fruit spikesedge, smallfruit spikerush |
Britton's spike-rush |
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Habit | Plants usually annual, tufted, sometimes mat-forming via proliferating and arching inflorescences (stoloniferous), sometimes entirely vegetative; rhizomes absent. | Plants usually annual, tufted, often stoloniferous; rhizomes absent. | ||||
Culms | often ascending or arching, quadrangular or broadly elliptic, 2–40 cm × 0.1–0.4(–0.6) mm, soft. |
ascending, quadrangular, sulcate (not sulcate in Eleocharis sp. |
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Leaves | distal leaf sheaths persistent or disintegrating, pale brown, green or red-brown, streaked or mottled red-brown or purple, translucent, membranous, apex narrowly acute. |
distal leaf sheaths persistent or fugaceous, pale brown or green, sometimes streaked red-brown, membranous to translucent, apex acute to acuminate. |
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Spikelets | 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. |
basal spikelets absent; often proliferous, ellipsoid to ovoid, terete, 2–10.5 × 1–2.8 mm, apex acute; proximal scale empty, persistent, amplexicaulous, dissimilar to floral scales, slightly longer, often resembling an involucral bract, elliptic or lanceolate, 1.4–2.7 × 0.8–1.2 mm, apex rounded, midrib markedly thickened and broad; subproximal scale with a flower; floral scales spiraled, 13–76, 9–13 per mm of rachilla, colorless or pale brown, streaked or mottled pale brown to red-brown, midribs sometimes green, ovate, elliptic, or obovate, 0.8–2.2 × 0.5–1 mm, papery or membranous, midrib evident to prominent, apex rounded. |
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Flowers | perianth bristles present or sometimes apparently absent; stamens 3; anthers 0.15–0.35; styles 3-fid. |
perianth bristles 5–6 or absent, appressed to achene, white, vestigial to shorter than achene, to 0.3 mm; spinules not evident at 45X; stamens 2–3; anthers 0.2–0.45 mm; styles 3-fid. |
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Achenes | 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. |
grayish to pale olive or yellowish, often minutely brown-spotted, obovoid, trigonous, angles prominent, 0.45–0.8 × 0.3–0.55 mm, apex constricted proximal to tubercle, smooth or finely pitted at 30X. |
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Tubercles | green or pale brown to red-brown, trigonous. |
gray, green, or yellowish, birettaform, trigonous, 0.05–0.1 × 0.15–0.3 mm. |
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Aff | . |
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Brittonii | ), 7–37 cm × 0.2–0.6 mm, soft to firm. |
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2n | = 10. |
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Eleocharis microcarpa |
Eleocharis brittonii |
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Phenology | Fruiting mid spring–winter. | |||||
Habitat | Freshwater, moist terrestrial sites, peaty ponds, swamps | |||||
Elevation | 0–100 m (0–300 ft) | |||||
Distribution |
AL; FL; GA; IN; LA; MA; MD; MI; MS; NC; NJ; PA; SC; TN; TX; VA; West Indies
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AL; AR; FL; GA; LA; MO; MS; SC; TN; TX
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Discussion | 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.) |
Preliminary studies suggest that Eleocharis brittonii may be comprised of two entities that may warrant taxonomic recognition, perhaps at the species level. Typical E. brittonii is usually robust, with floral scales pale brown and papery, bristles well developed, and achenes to 0.8 mm, clearly pitted at 30X. It is known from Alabama, Florida, Georgia, Louisiana, Mississippi, New Jersey, and South Carolina. The second variant is usually small with floral scales whitish with red-brown markings, bristles absent or poorly developed, and achenes not more than 0.6 mm, smooth at 30X. We have annotated specimens of this second variant E. sp. aff. brittonii, known from Arkansas, Florida, Georgia, Louisiana, Mississippi, Tennessee, and Texas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 23, p. 95. | FNA vol. 23. | ||||
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | E. microcarpa var. brittonii | |||||
Name authority | Torrey: Ann. Lyceum Nat. Hist. New York 3: 312. (1836) | Svenson ex Small: Man. S.E. Fl., 164. (1933) | ||||
Web links |