Carex sect. Heleoglochin
Fl. Belg., 146. 1827.
Plants densely cespitose, short-rhizomatous. Culms brown to dark brown at base, not more than 1 mm wide distally. Leaves: basal sheaths not fibrous; sheath fronts dotted red or copper, sometimes weakly transversely rugose, membranous; blades V-shaped in cross section when young, glabrous. Inflorescences compound, from evidently paniculate to often condensed, with numerous spikes; proximal bracts awl-shaped or bristlelike, others scalelike or absent, sheathless; lateral spikes androgynous or pistillate, sessile, without prophylls; terminal spikes androgynous. Proximal pistillate scales with apex acute to cuspidate. Perigynia usually spreading, strongly veined abaxially, obscurely veined or veinless adaxially, shortly stipitate, lance- to deltate-ovate or obovate, unequally biconvex or plano-convex in cross section, thick-walled or leathery, base tapered to rounded, with spongy tissue, margins acutely angled, apex ± abruptly beaked, glabrous; beak shortly bidentate, with abaxial suture. Stigmas 2. Achenes biconvex, smaller than bodies of perigynia; style deciduous, slightly thickened at base.
Temperate regions of North America, Eurasia, n Africa, Canary Islands, and Australasia.
Species 11 or 12 (4 in the flora).
Species of Carex sect. Heleoglochin are closely related to those of sections Multiflorae and Vulpinae; the three sections form a natural group characterized especially by the inflorescence tending to be compound. A distinctive morphologic characteristic of these groups (as well as of sect. Phaestoglochin) is the production of very short (slightly elongate in sect. Vulpinae), rather slender, tough, dark brown to blackish rhizomes; although seldom collected, these are sometimes visible as nubbins protruding from the base of the specimen. Plants that otherwise might key to sect. Heleoglochin should be sought in sections Divisae, Intermediae, or Ammoglochin if they lack red dots on the leaf sheaths and have relatively long anthers (ca. 2–4 instead of 1–2.5 mm).
|1||Inflorescence mostly 7–15 cm, proximal 3–9 branches well separated, basal 1 with 9–33(–48) spikes; perigynia deep olive green to brown at maturity, obpyramidal or broadly obovoid, body very abruptly contracted into beak 0.4–0.7 mm; leaf sheaths concave at mouth, not prolonged.||Carex decomposita|
|1||Inflorescence mostly 2–8 cm, proximal 1–5 branches obscure to ± separated, basal 1 with 2–21 spikes (or, occasionally, ca. 40 spikes in C. cusickii); perigynia golden brown to brownish black, lance-ovoid to ovoid (broader in the western C. cusickii), body tapered or abruptly contracted into beak 0.8–1.4 mm; leaf sheaths truncate to convex (concave in C. cusickii) and prolonged at mouth beyond base of blade.||> 2|
|2||Inner band of leaf sheath whitish except for reddish dots; inflorescence straight, little interrupted, proximal branches usually at least slightly overlapping 1 above; perigynia low-convex on adaxial face, ± spreading at maturity, not concealed by scales.||Carex diandra|
|2||Inner band of leaf sheath strongly copper colored toward summit (as well as red dotted); inflorescence commonly ± flexuous and interrupted, proximal branches often separated; perigynia plane on adaxial face distal to thick body, appressed to spreading at maturity, nearly or completely concealed by scales.||> 3|
|3||Broadest leaf blades not over 3 mm wide; sheath prolonged 2–8 mm beyond base of blade, continuous with short ligule to form collar of uniform length or longest on side opposite blade; perigynia dull; scales light reddish brown.||Carex prairea|
|3||Broadest leaf blades 4–6 mm wide; sheath prolonged 1–4(–6) mm beyond base of blade, tapering distally on adaxial side of blade and forming ligule 1.5–7(–12) times as long as adnate prolonged portion of leaf sheath; perigynia shiny; scales straw colored or reddish brown.||Carex cusickii|