Sp. Pl. 1: 87. 1753; Gen. Pl. ed. 5; 38, 1754.
Herbs, annual or perennial, often cespitose, rosulate. Roots: larger roots unbranched, pale, septate, thickened, spongy. Stems rarely sparingly branched, short or elongate. Leaves many ranked in flat or high spiral; blade basally pale, distally greener, linear-attenuate or triangular-acuminate, lingulate, narrowing gradually or abruptly from base, base noticeably lacunate, less distinctly so distally. Inflorescences: scape sheaths tubular, orifice oblique (often 2–3-cleft); scapes 1–several per rosette, glabrous; heads pale to dark, white, gray, or gray-brown, hemispheric to globose or short-cylindric; receptacle hairy or glabrous; involucral-bracts obscured or not obscured by inflorescence, pale to dark, chaffy or scarious; receptacular-bracts narrower, thinner than involucral-bracts, often scarious. Flowers mostly with staminate and pistillate on same plants, 2–3-merous; sepals 2 (–3), adnate to stipelike base, boatshaped, scarious, apex often covered with multicellular hairs, hairs mealy white or translucent, frequently club-shaped; petals 2 (–3), narrower, shorter than sepals, apex hairy, hairs club-shaped, glands adaxial, subapical, dark, rarely pale. Staminate flowers: androphore apically dilated stalk; petals separated from sepals by androphore, diverging as lobes from apex; stamens 3–4 or 6, 2–3 alternating with petals; apex of staminal column with 2–3 glands, glands unappendaged; filaments arising from androphore rim; anthers 2-locular, 4-sporangiate, dorsifixed, usually versatile, well exserted at anthesis, jet black (except in E. cinereum). Pistillate flowers: gynophore separating petals from sepals, stipelike; pistil 2 (–3) -carpellate; style 1, unappendaged, style-branches 2 (–3).
Mostly pantropic, mostly aquatic or on wet, mainly acidic substrates
Species ca. 400 (11 in the flora).
|1||Receptacle and/or base of flowers copiously hairy; some or most receptacular bracts and perianth parts with chalk white hairs; heads white, 5 mm or more in full flower or in fruit.||> 2|
|1||Receptacle and/or base of flowers glabrous or sparingly hairy; receptacular bracteoles and/or perianth glabrous or hairy, hairs club-shaped, clear or white; heads dark gray or white, usually less than 7.5 mm in full flower or in fruit.||> 4|
|2||Heads hard, very slightly flattened when pressed; scape sheaths shorter than most leaves; involucral bracts straw-colored, apex acute; receptacular bracteoles pale, apex narrowly acuminate; pistillate flower petals adaxially glabrescent; terminal cells of club-shaped hairs of perianth whitened, basal cells often uncongested, transparent; plants of moist but seldom aquatic or permanently wet situations||Eriocaulon decangulare|
|2||Heads soft, much flattened when pressed; scape sheaths longer than most leaves; involucral bracts gray or dark, apex rounded or obtuse; receptacular bracteoles gray to dark gray, apex acute; pistillate flower petals adaxially villous; all cells of club-shaped hairs on perianth mealy white; plants in aquatic or wet substrates.||> 3|
|3||Mature heads 10–20 mm wide; leaves 5–30 cm; petals of staminate flower conspicuously unequal||Eriocaulon compressum|
|3||Mature heads 5–10 mm wide; leaves (1–)2–5(–7) cm; petals of staminate flower nearly equal||Eriocaulon texense|
|4||Stamens 6, pistil 3-carpellate.||> 5|
|4||Stamens 4, pistil 2-carpellate||> 6|
|5||Anthers yellow; apex of receptacular bracteoles acute||Eriocaulon cinereum|
|5||Anthers black, apex of receptacular bracteoles obtuse||Eriocaulon microcephalum|
|6||Heads 4–10 mm wide at maturity; outer involucral bracts usually reflexed, obscured by bracteoles and flowers.||> 7|
|6||Heads seldom as wide as 5 mm; outer involucral bracts not reflexed, not obscured by bracteoles and flowers.||> 8|
|7||All bracts of staminate and pistillate flowers straw-colored or pale with grayish midzone; sepals of pistillate flowers basally pale, darkening distally to grayish, gray-green, or gray-brown; heads (young or mature) very pale; seeds faintly rectangular-reticulate, often papillate in lines; s coastal plain||Eriocaulon lineare|
|7||Inner involucral bracts, receptacular bracts, and sepals darkened, usually gray to near black; young heads dark; seeds very faintly reticulate, not papillate; n and/or montane||Eriocaulon aquaticum|
|8||Bracts straw-colored, greenish, or light gray to gray, dull, margins often erose or lacerate, apex blunt to obtuse; scapes linear; plants of brackish substrates||Eriocaulon parkeri|
|8||Bracts dark, gray to blackish, very lustrous, margins all nearly entire (except Eriocaulon nigrobracteatum), apex acute; scapes filiform; plants of acidic substrates.||> 9|
|9||Bracts narrowly ovate to oblong or spatulate, apex acute; bracts and perianth parts (except petals in some cases) glabrous; seed conspicuously pale-reticulate||Eriocaulon ravenelii|
|9||Bracts wider in outline, apex rounded or apiculate; bracts (margins and apex) and perianth hairy; seed not pale-reticulate.||> 10|
|10||Petals of pistillate flowers stipitate, suborbiculate-rhombic; outer involucral bracts straw-colored, inner and receptacular bracts dark gray, gray-green, or gray-brown||Eriocaulon koernickianum|
|10||Petals of pistillate flowers short-stipitate or nearly sessile, oblong; involucral and receptacular bracts blackish or with pale base||Eriocaulon nigrobracteatum|
"narrower" is not a number.