Eriocaulon

Linnaeus
Sp. Pl. 1: 87. 1753; Gen. Pl. ed. 5; 38, 1754.
Common names: Pipewort button-rods hat-pins eriocaulon
Etymology: derived from Greek erion, wool, and caulos, stalk
Treatment appears in FNA Volume 22.

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, boat-shaped, 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).

Distribution

Mostly pantropic, mostly aquatic or on wet, mainly acidic substrates.

Discussion

Species ca. 400 (11 in the flora).

Selected References

None.

Key

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