Eleocharis obtusa |
Eleocharis quadrangulata |
|
---|---|---|
blunt spike-rush, blunt spikesedge, broad spike spikerush, egg-shape spike-rush, éléocharide obtuse |
four-angle spikerush, square-stem spike-rush, square-stem spikesedge |
|
Habit | Plants perennial; rhizomes 1.5–4 mm thick, soft to hard, longer internodes 3–8 cm, scales 5–10 mm, tubers absent. | |
Culms | 3–50(–90) cm × 0.2–2 mm. |
acutely quadrangular, (30–)45–105 cm × (1–)2–5.4 mm, soft to firm, internally spongy, transverse septa incomplete; plants never forming filiform, flaccid culms. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent, membranous, apex narrowly acute to acuminate, sometimes prolonged into a bladelike portion to 8 cm. |
Spikelets | broadly ovoid (to ellipsoid or lanceoloid), apex rounded (to acute), (2–)5–13 × (2–)3–4 mm; floral scales 15–150+, 8–20 per mm of rachilla, orange-brown (to stramineous), elliptic, 1.5–2.5 × 1–1.5 mm, midribs seldom keeled, apex broadly rounded. |
not proliferous, (15–)20–76 × 3–5(–6) mm; rachilla joints bearing obscure winglike remnants of floral scales; proximal scale empty, amplexicaulous, (1–)2.2–5.4 mm; floral scales (28–)45–135, 2–3 per mm of rachilla, stramineous to pale brown, usually with pale to dark brown submarginal band, midrib region sometimes greenish, broadly obovate to ovate, (4–)4.5–6.2 × 2.8–5 mm, subcartilaginous, apex rounded to obtuse. |
Flowers | perianth bristles (5–)6–7, rarely 0, brown, stout, slightly to usually greatly exceeding tubercle; stamens usually 3; anthers brown to yellow, 0.3–0.6 mm; styles usually 3-fid and 2-fid in same spikelet. |
perianth bristles 6–7, whitish to brown, slender, often markedly unequal, shorter than achene or some equalling tubercle, sparsely retrorsely spinulose to smooth; anthers stramineous to red-brown, 2.3–2.9 mm; styles 3-fid, sometimes 2-fid. |
Achenes | 0.9–1.2(–1.3) × 0.7–0.9 mm. |
yellow or pale green to brown or purplish, biconvex, obovoid to obpyriform, 1.8–3 × 1.3–2 mm, almost smooth to markedly sculptured at 10–15X, each face with 19–38 rows of almost linear, transversely elongated cells, which are sometimes isodiametric at achene base, apex often constricted to neck 0.3–0.4 mm wide. |
Tubercles | deltoid 0.35–0.5 × (0.4–)0.5–0.8 mm, 1/3–2/3 as high as wide, 1/3–1/2 as high and 2/3–9/10 as wide as achene. |
dark brown or whitish, deltoid to high-pyramidal or lanceoloid, 0.7–1.5 × 0.4–1 mm, often spongy. |
2n | = 10. |
|
Eleocharis obtusa |
Eleocharis quadrangulata |
|
Phenology | Fruiting summer–fall. | Fruiting early summer–winter. |
Habitat | Fresh shores, marshes, disturbed places | Shallow water of fresh lake and pond shores, marshes |
Elevation | 10–1600 m [30–5200 ft] | 10–600 m [30–2000 ft] |
Distribution |
AL; AR; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WY; HI; BC; NS; ON; PE; QC
|
AR; CA; CT; DE; FL; GA; IL; IN; KY; LA; MA; MI; MO; MS; NC; NJ; NY; OH; OK; OR; PA; SC; TX; VA; WI; WV; ON; s to c Mexico
|
Discussion | Extremely uncommon plants of Eleocharis obtusa without perianth bristles may be called E. obtusa var. peasei (type from New Hampshire). Robust plants with distinct caudices, floral scales 2.5 mm, and achenes 1.2–1.3 mm (Eleocharis obtusa var. gigantea Fernald) are rare (specimens seen from the Washington-British Columbia border [type], Arkansas, and the Hawaiian Islands). Dwarf plants (E. obtusa var. jejuna Fernald, type from Maine), with unusually small achenes and floral scales, and tubercles often less than 0.5 mm wide, are occasional in the East and are easily confused with E. ovata and E. aestuum. A few specimens are intermediate with E. engelmannii. Eleocharis obtusa is sometimes treated as conspecific with E. ovata, which consistently differs in its mostly 2-fid styles, mostly two stamens, and especially its narrower tubercles (B. M. H. Larson and P. M. Catling 1996). Eleocharis macounii Fernald has been treated as a synonym of E. obutsa (H. K. Svenson 1957) but is more probably a hybrid between E. intermedia and E. obtusa (P. M. Catling and S. G. Hay 1993; see 34. E. intermedia). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
We have not seen voucher specimens for the reports of Eleocharis quadrangulata from Kansas. Plants with greenish achenes, longer bristles, and longer anthers than the average are known from Tennessee. The tubercles of Eleocharis quadrangulata are often spongy as in E. obtusetrigona. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 105. | FNA vol. 23, p. 120. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Scirpus obtusus, E. obtusa var. ellipsoidales, E. obtusa var. gigantea, E. obtusa var. jejuna, E. obtusa var. peasei | Scirpus quadrangulatus, E. quadrangulata var. crassior, Scirpus albomarginatus, Scirpus marginatus |
Name authority | (Willdenow) Schultes: Mant. 2: 89. (1824) | (Michaux) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 155. (1817) |
Web links |
|
|