Eleocharis obtusa |
Eleocharis pachycarpa |
|
---|---|---|
blunt spike-rush, blunt spikesedge, broad spike spikerush, egg-shape spike-rush, éléocharide obtuse |
black sand spikerush, broad fruit spikerush |
|
Habit | Plants perennial, forming dense clumps, often stoloniferous. | |
Rhizomes | present, caudexlike, mostly concealed by crowded culms, vertical or ascending, 2 mm thick; internodes very short, scales disintegrating to fibers, 4 mm, papery. |
|
Culms | 3–50(–90) cm × 0.2–2 mm. |
erect to ascending or arching, acutely quadrangular, deeply sulcate, 7–50 cm × 0.3–0.5 mm, smooth, firm. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent, proximally brown or reddish, distally stramineous to green, thickly membranous, apex acute or subacute. |
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. |
basal spikelets absent; often proliferous, ovoid, terete, 3–10 × 2–3 mm, apex acute; proximal scale empty, amplexicaulous, similar to floral scales; subproximal scale with a flower; floral scales spiraled, 8–15, 4 per mm of rachilla, orange-brown, midrib region broadly stramineous or like flanks, ovate, 2–3 × 1.2–2 mm, membranous, midrib evident to prominent, apex acute (to rounded). |
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 or fewer, stramineous, unequal, some or most equaling achene, spinules obscure, sparse, retrorse, sharply acute. |
Stamens | 3; anthers 1.2–1.5 mm. |
|
Styles | 3-fid. |
|
Achenes | 0.9–1.2(–1.3) × 0.7–0.9 mm. |
stramineous, broadly obpyriform, equilaterally trigonous, angles evident, blunt, 0.9–1.1 × 0.7–0.9 mm, apex nearly truncate, smooth or obscurely papillose or rugulose at 20X. |
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. |
stramineous, pyramidal, trigonous, usually acute, proximally trilobed, the lobes decurrent on achene, 0.5–0.9 × 0.7–0.9 mm. |
2n | = 10. |
|
Eleocharis obtusa |
Eleocharis pachycarpa |
|
Phenology | Fruiting summer–fall. | Fruiting late spring–summer. |
Habitat | Fresh shores, marshes, disturbed places | Fresh shores, streambeds, groundwater seeps |
Elevation | 10–1600 m [30–5200 ft] | 100–1400 m [300–4600 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
|
CA; NV; South America (Argentina, Chile) [Introduced in North America; introduced in Australia]
|
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.) |
H. K. Svenson (1957) placed Eleocharis pachycarpa in ser. Sulcatae Svenson. Contrary to his statement that perianth bristles are often lacking, they are present in all of the specimens we have seen. Superficially similar to E. bolanderi, from which it may readily be distinguished by its oblique leaf sheath summits, 4-angled culms, pyramidal tubercles, and often proliferating spikelets. The earliest North American specimen we have seen was collected in 1919 in Tuolumne County, California. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 105. | FNA vol. 23, p. 91. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Scirpus obtusus, E. obtusa var. ellipsoidales, E. obtusa var. gigantea, E. obtusa var. jejuna, E. obtusa var. peasei | |
Name authority | (Willdenow) Schultes: Mant. 2: 89. (1824) | E. Desvaux: in C. Gay, Fl. Chil. 6: 174. (1853) |
Web links |
|