Eleocharis engelmannii |
Eleocharis reverchonii |
|
---|---|---|
Engelman spikerush, Engelmann's spike-rush, Engelmann's spikesedge, englemann's spike-rush |
Reverchon's spikerush |
|
Habit | Plants perennial; rhizomes sometimes not evident, 0.3–0.5 mm thick, internodes 3–11 mm, scales not evident. | |
Culms | 2–40 cm × 0.5–1.5(–2) mm. |
sometimes arched, smooth or obscurely 4- or 5-angled or -ridged, terete or slightly compressed, 6–25 cm × 0.15–0.3 mm, soft to firm. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent, red proximally, colorless distally, closely sheathing, apex blunt. |
Spikelets | lanceoloid to subcylindric or ovoid, 5–10(–20) × 2–3(–4) mm, apex acute (to rounded); proximal scale empty, encircling ca. 2/3 of culm; floral scales 25–100(–200), 8–12 per mm of rachilla, orangebrown to stramineous, 2(–2.5) × 1–1.3 mm, midribs mostly keeled, ovate, apex narrowly rounded to subacute. |
ovoid, 2–6 × 1–2 mm, apex acute; scales 5–15, 5 per mm of rachilla, bright red-brown, midrib region green to stramineous, ovate, 1.5–1.7 × 1 mm, midrib keeled to obscure, apex blunt to acute. |
Flowers | perianth bristles present or often absent, 5–8, brown, stout, rudimentary to slightly exceeding tubercle; stamens (2–)3; anthers brown to yellow, 0.3–0.7(–1) mm; styles 2–3-fid. |
perianth bristles absent; anthers 0.5–1 × 0.2 mm. |
Achenes | 0.9–1.1(–1.5) × 0.7–1.1 mm. |
with angles plus longitudinal ridges ca. 8–9, obscure to rather prominent, obovoid to obpyriform, much less than 2 times longer than wide, 0.55–0.6 × 0.3–0.4 mm, trabeculae 20–30, rather obscure and crowded. |
Tubercles | depressed, subdeltoid, 0.1–0.3(–0.4) × 0.6–0.9(–1) mm, 1/10–2/5 as high as wide, 1/4 or less as high as achene, 9/10 as wide as achene, very rarely 2/5 as high as achene (in E. engelmannii var. robusta). |
brownish to whitish, pyramidal to depressed, 0.1–0.15 × 0.1–0.2 mm. |
2n | = 10. |
|
Eleocharis engelmannii |
Eleocharis reverchonii |
|
Phenology | Fruiting spring–fall. | Fruiting late winter–spring (Feb–Apr). |
Habitat | Fresh shores, marshes, disturbed places | Wet soil of ponds, marshes, grasslands, ditches |
Elevation | 30–2400 m (100–7900 ft) | 10–200 m (0–700 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; IA; ID; IL; IN; KS; KY; MA; MD; MI; MN; MO; MS; MT; ND; NE; NH; NJ; NM; NY; OH; OK; OR; PA; RI; TN; TX; VA; WA; WI; WV; AB; BC; MB; ON
|
TX |
Discussion | Robust plants known only from Missouri and described as Eleocharis engelmannii var. robusta have well-developed caudices, culms to 2 mm wide (pressed), spikelets to 2 cm, floral scales to 2.5 mm and slightly cartilaginous, styles mostly trifid, achenes to 1.5 × 1 mm, and tubercles 0.3–0.5 × 0.7–1 mm and to 2/5 as high as achene. Some specimens are intermediate between E. engelmannii and E. obtusa, or rarely with E. lanceolata. I have not seen specimens to verify literature reports of E. engelmannii from Manitoba, Connecticut, Delaware, Idaho, New Hampshire, North Carolina, Oregon, Rhode Island, South Carolina, South Dakota, or Vermont. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Eleocharis reverchonii perhaps should be treated as a variety or subspecies of E. acicularis. One collection (three sheets at KSC) from Calhoun county in southeastern Texas is apparently the only known example within E. subg. Scirpidium with proliferous spikelets. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 104. | FNA vol. 23, p. 110. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae | Cyperaceae > Eleocharis > subg. Scirpidium |
Sibling taxa | ||
Synonyms | E. engelmannii var. detonsa, E. engelmannii var. monticola, E. engelmannii var. robusta, E. monticola, E. monticola var. leviseta, E. ovata var. detonsa | |
Name authority | Steudel: Syn. Pl. Glumac. 2: 79. (1855) | Svenson: Rhodora 31: 203, fig. 27. (1929) |
Web links |
|