Eleocharis geniculata |
Eleocharis robbinsii |
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bent spike-rush, Canada spikesedge, capitate spike-rush |
Robbin's sppike-rush, Robbins' spikerush, Robbins' spikesedge, éléocharide Robbins |
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Habit | Plants tufted, without creeping rhizomes. | 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. |
Culms | to 45 cm × 0.2–1 mm. |
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. |
Leaves | distal leaf sheaths persistent, firm, distally tightly sheathing, apex acute. |
distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate. |
Spikelets | orbicular to ovoid, 1–9 × 1–4 mm, apex rounded to acute; proximal scale without flower, not amplexicaulous; floral scales to 125, 11–14 per mm of rachilla, tightly appressed, dark red-brown to stramineous, ovate to elliptic, 0.8–3 × 0.6–2(–2.3) mm, membranous to cartilaginous, apex rounded to acute. |
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. |
Flowers | perianth bristles (0–)4–8, typically 7, red-brown, rarely whitish, vestigial to much exceeding tubercle, typically equaling achene, spinules few to dense; styles 2-fid. |
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. |
Achenes | brown ripening to black, biconvex, orbicular to obpyriform, 0.5–1.1 × 0.3–0.7 mm, apex rarely constricted proximal to tubercle, very finely reticulate at 40X. |
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. |
Tubercles | stramineous to whitish, umbonate to subconic, 0.2–0.4 × 0.2–0.5 mm, apex rounded to acute. |
stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm. |
2n | = 10. |
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Eleocharis geniculata |
Eleocharis robbinsii |
|
Phenology | Fruiting spring–winter (Mar–Dec). | Fruiting late spring–late fall. |
Habitat | Brackish creeks, canal banks, dune depressions, hammocks, irrigation ditches, lakeshores, lagoons, mangrove thickets, maritime mud flats, ditches, salt marshes | Shallow waters of fresh lakes and ponds with sandy-peaty soils |
Elevation | 0–1500 m (0–4900 ft) | 10–500 m (0–1600 ft) |
Distribution |
AL; AZ; CA; FL; GA; IL; IN; LA; MI; MS; NE; NM; NV; OH; OK; PA; TX; ON; Mexico; Central America; South America; West Indies; Bermuda; Asia; Africa; Pacific Islands
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AL; CT; DE; FL; GA; MA; ME; MI; MN; NC; NH; NJ; OH; SC; VA; WI; NB; NS; ON; QC
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Discussion | The name Eleocharis caribaea (Rottbøll) S. F. Blake is considered by most contemporary authorities to be misapplied (K. L. Wilson 1990). Eleocharis geniculata has been reported from South Carolina; I have not seen a voucher. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 23, p. 101. | FNA vol. 23, p. 117. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Maculosae | Cyperaceae > Eleocharis > subg. Limnochloa |
Sibling taxa | ||
Synonyms | Scirpus geniculatus, E. capitata, E. caribaea, E. dispar | |
Name authority | (Linnaeus) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 150. (1817) | Oakes: Mag. Hort. Bot. 7: 178. (1841) |
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