Plants densely cespitose or forming loose colonies, short-rhizomatous; shoots both vegetative and flowering. Culms usually maroon, or less often brown, tan, or pale green at base. Leaves: basal sheaths usually bladeless, sometimes fibrous; sheath fronts white-hyaline to brown-hyaline, rarely membranous; blades M-shaped in cross-section when young, adaxial side with 2 lateral-veins more prominent than midvein; widest leaves not more than 13 mm, glabrous or pubescent, not septate-nodulose. Inflorescences racemose, with 3–7 (–16 in C. obispoensis) spikes; proximal nonbasal bracts leaflike, except in C. castanea, sheaths usually longer than 5 mm, except in C. castanea, C. misera, and C. sprengelii; lateral spikes erect or nodding, pistillate, with no more than 50 perigynia, the distal ones androgynous, rarely the proximal 1 gynecandrous, pedunculate, peduncle 1+ cm, prophyllate; terminal spike erect, staminate, gynecandrous, or rarely androgynous. Proximal pistillate scales green with broad hyaline margins, hyaline portions white or, more often, suffused with maroon or chestnut-brown, apex obtuse to acuminate or awned, awn not more than 3 mm, glabrous, margins sometimes ciliate. Perigynia erect or ascending, veined or veinless on faces, with 2 strong marginal veins, sometimes stipitate, narrowly lanceovoid to fusiform to oblong-ovoid, trigonous or rounded-trigonous, 2–10 mm, more than 3 times as long as wide, base tapering or rounded, apex tapering or abruptly contracted to beak or beakless, glabrous or pubescent; beak 0.5–3 mm, ca. 1/2 length of body, orifice entire to bidentate, teeth to 1 mm. Stigmas 3. Achenes trigonous, smaller than to almost as large as bodies of perigynia; style deciduous. x = 16–30.

Distribution

North America, Mexico, Central America, Europe, Asia, Africa

Discussion

Species ca. 50–60 (20 in the flora).

Carex sect. Hymenochlaenae has been variously circumscribed and is used here in the broad sense, following A. A. Reznicek (1986), although it is clear that sect. Hymenochlaenae so defined is not monophyletic (M. J. Waterway 1999). Groups segregated by K. K. Mackenzie (1931–35, parts 2–3, pp. 277–299) as sect. Gracillimae, sect. Sylvaticae, and sect. Longirostres are included here but sect. Capillares is treated separately. A. A. Reznicek (1986) chose Carex cherokeensis as the lectotype for sect. Hymenochlaenae. Among the species treated here, only C. obispoensis and probably C. sprengelii are clearly closely related to C. cherokeensis. All three species differ from the others by having multiple androgynous spikes and a tendency for multiple spikes at each node of the inflorescence and by lacking proximal bladeless sheaths. Species 307–314, 316–322 form a much larger group of closely related species, which when grouped with sect. Porocystis are apparently monophyletic (M. J. Waterway 1999), but further study is required before the sectional rearrangements and nomenclatural changes can be made. Those species share the maroon basal bladeless sheaths, a single terminal staminate or gynecandrous spike, the tendency to have overwintering basal leaves, and most frequently have red crystalline inclusions on the sheaths, perigynia, and sometimes the pistillate and staminate scales. In many species, basal leaves on the vegetative culms tend to be wider, sometimes much wider than the cauline leaves on the flowering culms, so care must be taken to observe the basal leaves, especially those on the vegetative culms when assessing leaf width. Sporadic hybrids among species within the group are quite frequent. Carex prasina, C. sylvatica, and C. assiniboinensis are anomalous within the section for different reasons and have no more affinity with each other than with the core species. Because their placement elsewhere is also problematic they are retained in this treatment. Carex sect. Capillares also appears to form a distinct monophyletic group that is not closely related to the other species treated here.

Selected References

None.

Lower Taxa

Carex aestivalis, Carex arctata, Carex assiniboinensis, Carex castanea, Carex cherokeensis, Carex davisii, Carex debilis, Carex formosa, Carex gracillima, Carex gynodynama, Carex hirtissima, Carex mendocinensis, Carex misera, Carex obispoensis, Carex oxylepis, Carex prasina, Carex roanensis, Carex sprengelii, Carex sylvatica, Carex venusta

Key

1	Terminal spike staminate; lateral spikes staminate, androgynous, or pistillate; base of culms tan, brown, or ivory.	> 2
1	Terminal spike staminate or gynecandrous; lateral spikes pistillate, gynecandrous or rarely distal spike staminate; base of culms usually covered with dark maroon bladeless sheaths (often missing or very short in C. prasina).	> 5
2	Plants without rhizomes or with very short ones, densely cespitose.	> 3
2	Plants with short-creeping rhizomes, loosely cespitose or colonial.	> 4
3	Perigynia 5–8 × 1.3–2.7 mm, gradually tapering to beak, 12–20-veined and evenly short pubescent, loosely enveloping achenes; flowering culms more than 1.3 mm wide and bearing 5+ lateral pistillate spikes; California.	Carex obispoensis
3	Perigynia 4.5–6 × 1.4–1.8 mm, abruptly narrowed to elongate beak, 2-ribbed but otherwise veinless or nearly so, glabrous, tightly enveloping achenes; flowering culms less than 1.2 mm wide and bearing 2–4 lateral pistillate spikes; e North America.	Carex sylvatica
4	Perigynium abruptly narrowed to beak as long as body; basal sheath fibrous.	Carex sprengelii
4	Perigynium more gradually narrowed to beak about 1/2 as long as body; basal sheath not fibrous or not conspicuously so.	Carex cherokeensis
5	Perigynia 2-ribbed but otherwise veinless or nearly so, green to yellow at maturity.	> 6
5	Perigynia 2-ribbed and veined between ribs, often conspicuously so, green to olive-green at maturity, usually red dotted.	> 7
6	Pistillate spikes densely flowered with perigynia strongly overlapping, more than 10 per spike; perigynia green, membranous, tapered gradually to bent beak, surface smooth and glabrous.	Carex prasina
6	Pistillate spikes sparsely flowered with perigynia barely overlapping, fewer than 10 per spike; perigynia yellow at maturity, cartilaginous, tapered gradually to straight beak, surface pubescent and roughened distally.	Carex assiniboinensis
7	Perigynia fusiform to narrowly lance-ovoid, longer than 5 mm including elongate beak; leaves generally less than 5 mm wide; leaf sheaths usually glabrous, at least on back.	> 8
7	Perigynia ovoid-oblong to lance-ovoid, 2–6 mm (mostly 5 mm or less) tapering to beak shorter than body or beakless; leaves 2.5–12 mm wide; leaf sheaths glabrous or pubescent.	> 9
8	Lateral pistillate spikes linear, 25–80 × 2–3 mm; pistillate flowers attached 2–9 mm apart, each perigynium strongly overlapping only the 1 immediately above; perigynia 4.5–9.5 mm; pistillate scales white-hyaline with green midrib, less than 1/2 as long as mature perigynia.	Carex debilis
8	Lateral pistillate spikes cylindric, 10–50 × 4–5 mm; pistillate flowers usually attached 1–3 mm apart, each perigynium strongly overlapping at least 2 perigynia above; perigynia 4.6–9 mm; pistillate scales chestnut-hyaline with green midrib, at least 1/2 as long as mature perigynia.	Carex venusta
9	Terminal spike usually gynecandrous, rarely staminate.	> 10
9	Terminal spike usually staminate, rarely gynecandrous.	> 15
10	Perigynia 2–4 mm, beakless or nearly so; pistillate spikes linear, 10–70 × 2–3.5 mm, usually longer than 40 mm.	> 11
10	Perigynia at least 3.5 mm, apex tapering to abrupt beak; beak less than 0.7 mm; pistillate spikes cylindric, 10–50 × 3–6 mm.	> 13
11	Leaf sheaths glabrous or sparsely short-pubescent; leaf blades 3–9 mm wide.	Carex gracillima
11	Leaf sheaths pubescent, leaf blades less than 4.5 mm wide.	> 12
12	Perigynia glabrous; achenes 2–3.2 mm.	Carex aestivalis
12	Perigynia pubescent; achenes 3–4 mm.	Carex roanensis
13	Bract of proximal pistillate spike usually longer than entire inflorescence, 2–6 mm wide; pistillate scales cuspidate or with rough awns nearly as long as body of scale; perigynia 4.5–6 mm.	Carex davisii
13	Bract of proximal pistillate spike not usually exceeding inflorescence, 1.5–4.5 mm wide; pistillate scales acute to mucronate or with awns much shorter than body of scale; perigynia 3.5–5 mm.	> 14
14	All spikes gynecandrous, lateral spikes with at least 1 staminate flower at base; peduncles longer than pistillate spikes.	Carex formosa
14	Only terminal spike gynecandrous, lateral pistillate; peduncles shorter than pistillate spikes.	Carex oxylepis
15	Lateral pistillate spikes drooping at maturity, short cylindric to linear, 8–80 × 3–5 mm, on slender arching peduncles.	> 16
15	Lateral pistillate spikes erect at maturity, narrowly oblong to cylindric, to 25 × 2.5–9 mm, on stiff peduncles.	> 17
16	Pistillate spikes linear, 25–80 × 3–4 mm; proximal bract sheaths longer than 10 mm; leaf blades glabrous; perigynia distinctly stipitate.	Carex arctata
16	Pistillate spikes short cylindric, 8–25 × 4–5 mm; proximal bract sheaths very short, often less than 2 mm; leaf blades pilose; perigynia acute at base, but not stipitate.	Carex castanea
17	Leaf blades 4 mm wide or less.	> 18
17	Leaf blades wider than 5 mm, the proximal often 9–10 mm wide.	> 19
18	Proximal inflorescence bracts with sheaths less than 5 mm; leaf blades less than 2 mm wide; leaf sheaths pubescent; perigynia pubescent distally; s Appalachian mountains.	Carex misera
18	Proximal inflorescence bracts with sheaths more than 8 mm; leaf blades 2–4 mm wide; leaf sheaths usually glabrous; perigynia glabrous or with a few stiff hairs on beak; California and Oregon.	Carex mendocinensis
19	Pistillate spikes crowded toward tip, at least the distal 2 strongly overlapping each other and the terminal staminate (rarely gynecandrous) spike; pistillate scales maroon to chestnut with green midrib, broadly obovate, often short-cuspidate.	Carex gynodynama
19	Pistillate spikes, at least proximal ones, usually remote from terminal staminate spike; only distal pistillate spike usually overlapping the terminal staminate spike, if any; pistillate scales green to golden brown, oblong, with green midrib extending to ciliate short-aristate tip.	Carex hirtissima

"shortened" is not a number.