Eleocharis montevidensis Kunth

The name Eleocharis montana was long misapplied to E. montevidensis. The type of E. palmeri, recognized as a species (H. K. Svenson 1957), is indistinguishable from specimens of E. montevidensis. Eleocharis montevidensis is extremely variable; the broadly rounded, usually wrinkled and recurved floral scales are diagnostic. Achenes often fail to form. Eleocharis montevidensis is apparently closely related to E. parishii, in which the floral scales are less densely placed on the rachilla and acute to rounded, and the spikelets are narrowly lanceoloid to cylindric. In the absence of achenes and rhizomes, some specimens of E. montevidensis are easily mistaken for E. tricostata.

Plants perennial, mat-forming; rhizomes evident, long, 0.7–2 mm thick, firm, cortex persistent, longer internodes 1–2 cm, scales often fugaceous, 6–8 mm, membranous, not fibrous. Culms terete or cross section elliptic or rectangular, with 5–10 blunt ridges when dry, 25–50 cm × 0.5–1.2 mm, firm to hard, spongy. Leaves: distal leaf sheaths persistent, not splitting, mostly proximally dark red, distally red to brown or green, thinly papery, apex usually red-brown, often callose, subtruncate to obtuse, tooth usually present on some or all culms, to 0.9 mm. Spikelets usually ovoid or ellipsoid to subcylin-dric, rarely lanceoloid, 4–12 × (1.5–)2–3 mm, apex rounded to acute; proximal scale amplexicaulous or clasping over 3/4 of culm, entire; subproximal scale empty or with flower; floral scales appressed in fruit, 30–100, 6–10 per mm of rachilla, orange-brown, midrib regions often greenish, oblong to ovate, 1.5–2.5 × 1–1.5 mm, apex entire, broadly rounded, sometimes acute in distal part of spikelet, usually horizontally wrinkled and recurved, often carinate in distal part of spikelet. Flowers: perianth bristles 5–6(–7), stramineous to medium brown, stout, often unequal, much shorter than to equaling achene, rarely all rudimentary; stamens 3; anthers dark yellow to stramineous, 0.8–1.5 mm; styles 3-fid or some 2-fid. Achenes falling with scales, dark brown, obovoid to obpyriform, compressed trigonous, angles evident to obscure, 0.7–1 × 0.65–0.8 mm, neck absent to sometimes long, finely rugulose at 10–30X, over 20 horizontal ridges in vertical series, and/or minutely cancellate at 20–30X. Tubercles brown to whitish, pyramidal, as high as wide or sometimes greatly depressed, (0.1–)0.25–0.3 × 0.2–0.3 mm. 2n = 20.

Ala., Ariz., Calif., Fla., Kans., La., Miss., N.Mex., N.C., Okla., S.C., Tex.; Mexico; South America.

Fruiting spring–fall.

Wet soil, fresh ponds, lakes, streams, springs, seeps, marshes, ditches, grasslands; 0–2300m.

Eleocharis arenicola Torrey; E. montana (Kunth) Roemer & Schultes subsp. montevidensis (Kunth) Osten; E. palmeri Svenson

Eleocharis palmeri Svenson, Rhodora 34 : 223. 1932
Culms rather soft, 1.5-2 dm. high, erect from a ligneous rhizome; sheaths truncate at the apex, mucronate ; spikelets cylindric-ovoid, obtuse, 3-8 mm. long ; scales ovate-oblong, obtuse, pale brown with greenish midrib, hyaline at the margin and frequently emarginate; style trifid; stamens 3; achene 1-1.3 mm. long, shining brown, pyriform, obtusely trigonous, nearly smooth under magnification ; style-base pyramidal, acute, one-fourth as long as the achene ; bristles white, equaling the achene. Type locality : West margins of the Pecos River, in deep limestone canyon, near the Rio Grande, Valverde County, Texas (E. J. Palmer 33464). Distribution : Known only from the type collection.

Eleocharis montevidensis Kunth, Enum, PI. 2: 144. 1837
Eleocharis arenicola Torr. ; Engelm. & Gray, Bost. Jour. Nat. Hist. 5 : 237. 1845. (Texas.)
Limnochloa montevidensis Nees in Mart. Fl. Bras. 2}: 99. 1842.
Eleocharis montana sensu Britton, Jour. N. Y. Micr. Soc. 5: 109. 1889, and of many later
authors. Not E. montana (H.B.K.) R. & S. Trichophyllum arenicolum House, Am. Midi. Nat. 6 : 204. 1920. Heleocharis montana subsp. H. montevidensis Osten, Anal. Mus. Hist. Nat. Montevideo II. 3 :
183. 1931.
Culms erect from extensively creeping reddish rootstocks, 0.5-4.5 dm. high, rigid, striate ; upper sheath deep brown at the base, usually becoming stramineous toward the truncate apex; spikelets ovoid to oblong, blunt, 4-13 mm. long, many-flowered; scales ovate, obtuse, brownish or yellowish, with a hyaline margin ; style trifid ; achene 1 mm. long, obovoid, triangular, with blunt angles, golden-yellow to brown, with a minutely punctulate, glossy surface ; style-base conic, short, sessile at the apex of the achene, or sometimes with a slight constriction; bristles 4-6, brown, toothed, equaling or shorter than the achene.
Type locality: Montevideo, Uruguay {Humboldt).
Distribution : Chiefly in wet sand : South Carolina to Florida, west to California ; Mexico ; southern Brazil ; Uruguay ; Argentina.

Eleocharis montevidensis is a species of spikesedge known by the common name sand spikerush. It is a widespread coastal plant native to the Americas. It grows in moist, sandy spots in many habitat types, including lakes, riverbanks, wet meadows, and springs. It has a disjunct distribution, in North America (southern United States from California to the Carolinas, Mexico, Guatemala, Honduras) and South America (Brazil, Peru, Argentina, Uruguay).

Eleocharis montevidensis là loài thực vật có hoa trong họ Cói. Loài này được Kunth mô tả khoa học đầu tiên năm 1837.