Eleocharis robbinsii |
Eleocharis atropurpurea |
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Robbin's sppike-rush, Robbins' spikerush, Robbins' spikesedge, éléocharide Robbins |
purple spike-rush |
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Habit | Plants perennial; rhizomes (0.5–)1–2 mm thick, longer internodes 2–3 cm, scales 5–7 mm; tubers sometimes present, apical, ovoid, 4–8 × 3–4 mm. | Plants tufted, without creeping rhizomes. |
Culms | acutely trigonous; spikelet-bearing culms 16–70 cm × 0.7–0.9 mm; when submersed plants often forming numerous, filiform, flaccid culms without spikelets, sometimes with whorls of slender branches, 0.1–0.3 mm wide; soft, sometimes septate-nodulose when aquatic, internally spongy, transverse septa incomplete. |
2–12(–19) cm × 0.2–0.4 mm. |
Leaves | distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate. |
distal leaf sheaths firm, distally tightly sheathing, apex acute. |
Spikelets | sometimes proliferous (when submerged), 9–33 × 1.5–3 mm; rachilla joints bearing prominent winglike remnants of floral scales; proximal scale with a flower, amplexicaulous, (5–)6–9.8 mm; floral scales 4–18, 0.5–1 per mm of rachilla, stramineous to pale brown, often minutely dotted reddish, without or rarely with darker submarginal band, narrowly ovate to lanceolate, 5–7.8 × 2–3 mm, thickly papery, membranous toward margins, apex narrowly rounded to acute. |
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. |
Flowers | perianth bristles 6–7, stramineous to reddish brown, proximally slightly flattened, subequal to equal, much exceeding to rarely shorter than achene, 3–5 mm, retrorsely spinulose; anthers yellow to reddish, 1.6–3.2 mm; styles 3-fid. |
perianth bristles (0–)4–6, typically 4, colorless to whitish, vestigial to 1/2 as long as achene, smooth or spinuliferous; styles 2-fid. |
Achenes | stramineous or medium brown, biconvex or compressed trigonous, narrowly obpyriform, 1.9–2.6 × 1–1.4 mm, adaxial face with 15–22 rows of rectangular, transversely elongated or nearly isodiametric cells, clearly sculptured at 10–15X, apex usually conspicuously constricted to short neck 0.4–0.7 mm wide, usually wider at tubercle base. |
black, obovoid, biconvex, 0.3–0.5 × 0.3–0.4 mm, apex often constricted proximal to tubercle, smooth at 40X. |
Tubercles | stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm. |
stramineous to whitish, umbonate to subconic, 0.1–0.2 × 0.1–0.2 mm, apex acute. |
2n | = 20. |
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Eleocharis robbinsii |
Eleocharis atropurpurea |
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Phenology | Fruiting late spring–late fall. | Fruiting summer–fall (Jun–Sep). |
Habitat | Shallow waters of fresh lakes and ponds with sandy-peaty soils | Canal banks, hammocks, irrigation ditches, lake and pond margins, maritime shores, rice fields |
Elevation | 10–500 m (0–1600 ft) | 0–1800 m (0–5900 ft) |
Distribution |
AL; CT; DE; FL; GA; MA; ME; MI; MN; NC; NH; NJ; OH; SC; VA; WI; NB; NS; ON; QC
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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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Discussion | I have not seen voucher specimens for literature reports of Eleocharis robbinsii from Indiana, Pennsylvania, or Rhode Island. Plants from South Carolina with the achene surface cells nearly isodiametric, the achene apex spongy, and the anthers to 3.2 mm may represent an undescribed taxon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 23, p. 117. | FNA vol. 23, p. 102. |
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Maculosae |
Sibling taxa | ||
Synonyms | Scirpus atropurpureus | |
Name authority | Oakes: Mag. Hort. Bot. 7: 178. (1841) | (Retzius) J. Presl & C. Presl: in C. B. Presl, Reliq. Haenk. 1: 196. (1828) |
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