1	Spike single, terminal		(2)
+	Spikes 2 to numerous, usually 1 to several spikes borne in an involucral bract sheath, rarely arranged in compound inflorescence		(8)
2 (1)	Nutlets biconvex or plano-convex, stigmas 2		(3)
+	Nutlets trigonous, stigmas 3		(4)
3 (2)	Spikes bisexual, androgynous; utricles not spongy at base.		51 C. sect. Capituligerae
+	Spikes unisexual; utricles spongy at base.		52 C. sect. Physoglochin
4 (2)	Female glumes early deciduous; utricles downward reflexed in maturity, lateral veins not more conspicuous than veins on abaxial surface; regressive branch rachilla conspicuous, usually longer than nutlets.		46 C. sect. Leucoglochin
+	Female glumes deciduous at same time as utricles or later than utricles; utricles not distinctly downward reflexed in maturity, lateral veins more conspicuous than veins on abaxial surface; without regressive branch rachilla, or if with regressive branch rachilla then rachilla shorter than nutlets		(5)
5 (4)	Spikes shortly cylindric to capitate		(6)
+	Spikes linear or linear-cylindric, rarely only female spikes so		(7)
6 (5)	Nutlets with regressive branch rachilla at base.		47 C. sect. Rupestres
+	Nutlets without regressive branch rachilla at base.		48 C. sect. Rarae
7 (5)	Utricles shortly beaked (beak not over 1 mm), veins obscure on abaxial surface.		49 C. sect. Grallatoriae
+	Utricles long beaked (beak over 1 mm), veins conspicuous on abaxial surface.		50 C. sect. Rhizopodae
8 (1)	Utricles plano-convex or biconvex; stigmas 2		(9)
+	Utricles trigonous; stigmas 3		(13)
9 (8)	Involucral bracts sheathed; female spikes sparsely flowered, rarely slightly densely flowered.		45 C. sect. Graciles
+	Involucral bracts without sheaths; female spikes densely many flowered		(10)
10 (9)	Spikes pedunculate, ± pendent		(11)
+	Spikes nearly sessile or only lowermost or basal spike rather long pedunculate		(12)
11 (10)	Spikes 2-6 borne in every involucral bract sheath on inflorescence.		44 C. sect. Tuminenses
+	Spikes solitary in every involucral bract sheath on inflorescence.		43 C. sect. Praelongae
12 (10)	Utricles distinctly beaked, beak 0.5-1.5 mm, 2-toothed at orifice.		42 C. sect. Forficulae
+	Utricles beakless or shortly beaked, truncate or emarginate at orifice.		41 C. sect. Phacocystis
13 (8)	Utricles nearly beakless or with short beak, truncate, emarginate, or very shortly 2-toothed at orifice		(14)
+	Utricles with a long beak or medium-sized beak (beak rather short in C. sect. Paludosae), long or shortly 2-toothed at orifice, rarely subtruncate or very shortly toothed		(28)
14 (13)	Female spikes densely flowered; involucral bracts usually without sheath or only very shortly sheathed		(15)
+	Female spikes sparsely flowered; involucral bracts usually sheathed		(20)
15 (14)	Female spikes remote, pedunculate		(16)
+	Female spikes contiguous or rather congregate, rarely lower 1 or 2 remote, without peduncle or very shortly pedunculate, rarely lowermost one rather long pedunculate		(17)
16 (15)	Male spikes 2-6 (only 1 male spike in C. inanis); utricles hispidulous or scabrous.		15 C. sect. Hirtae
+	Male spike solitary, terminal; utricles glabrous.		16 C. sect. Anomalae
17 (15)	Involucral bracts leaflike or lower ones leaflike, rarely setaceous; terminal spike gynaecandrous, rarely male.		11 C. sect. Racemosae
+	Involucral bracts scale-shaped or lower ones linear, upper ones scale-shaped; terminal spike male		(18)
18 (17)	Female glumes red-brown or dark brown; utricles glabrous, usually shiny, obliquely truncate at orifice of beak; style base thickened.		14 C. sect. Lamprochlaenae
+	Female glumes brown or brownish; utricle hirtellous or papillate, emarginate or very shortly 2-toothed at orifice of beak		(19)
19 (18)	Utricles papillate; style base thickened.		12 C. sect. Glauciformes
+	Utricles hirtellous; style base not thickened.		13 C. sect. Acrocystis
20 (14)	Utricles glabrous or scabrid		(21)
+	Utricles pubescent or hispidulous, rarely glabrous		(24)
21 (20)	Leaf blades usually revolute at margins; involucral bracts sheathlike, without blades; male spike few flowered; style base thickened and globose.		22 C. sect. Albae
+	Leaf blades flat; involucral bracts leaflike or spathelike, with short blades; male spike many flowered; style base not thickened		(22)
22 (21)	Culms lateral; leaf blades rather broad, 6-30 mm wide (very few species with 3-6 mm wide blades); spikes bisexual, androgynous; female glumes pale or reddish brown.		25 C. sect. Siderostictae
+	Culms central; leaf blades rather narrow, 2-5 mm wide; spikes unisexual; female glumes ferruginous-brown or yellow-brown		(23)
23 (22)	Involucral bracts shortly sheathed; female spikes densely flowered, slenderly pedunculate, usually pendulous; style exserted from utricle.		23 C. sect. Limosae
+	Involucral bracts long sheathed; female spikes sparsely flowered, slightly thickly pedunculate, erect; style included in utricle (only stigmas exserted).		24 C. sect. Paniceae
24 (20)	Involucral bracts spathelike, without blade, rarely leaflike; nutlets not thickened at apex into annulate shape; style base slightly thickened or not thickened, rarely thickened and conic		(25)
+	Involucral bracts with short blades; nutlets thickened at apex into annulate shape; style base thickened into different shapes		(26)
25 (24)	Involucral bracts leaflike, rarely sheathlike; spikes bisexual, androgynous; utricles subleathery or papery; style base thickened and conic.		20 C. sect. Radicales
+	Involucral bracts spathelike, rarely sheathlike; spikes unisexual, terminal spike male, lateral spikes female; utricles membranous; style base thickened or not thickened.		21 C. sect. Clandestinae
26 (24)	Nutlets with persistent and bent style base at apex.		17 C. sect. Cryptostachyae
+	Nutlets without persistent style base at apex, or if nutlets with persistent style base then style base straight or thickened into cucullate shape		(27)
27 (26)	Nutlets with ± cylindric style base, concave at apex, persistent style base not thickened into cucullate shape.		18 C. sect. Lageniformes
+	Nutlets ± thickened into disk shape, not concave at apex, persistent style base thickened into cucullate shape.		19 C. sect. Mitratae
28 (13)	Leaf blades with transverse septate nodes between longitudinal veins		(29)
+	Leaf blades without transverse septate nodes between longitudinal veins		(33)
29 (28)	Utricles ± hispidulous or pubescent, rarely glabrous or ciliate on margins of beak		(30)
+	Utricles glabrous		(31)
30 (29)	Female glumes ovate or broadly ovate, apex acute, mucronate; utricles obtusely trigonous, ca. 4 mm, rarely 5 mm, shortly beaked, shortly 2-toothed at orifice.		39 C. sect. Occlusae
+	Female glumes lanceolate, narrowly ovate, or oblong-ovate (broadly ovate in C. latisquamea), apex acuminate, aristate or mucronate; utricles slightly inflated trigonous or inflated trigonous, 5-10 mm, rarely ca. 4 mm, medium to long beaked, ± long to long 2-toothed at orifice.		40 C. sect. Carex
31 (29)	Female glumes long aristate; utricles eventually horizontally patent or downward reflexed, obtusely trigonous, long beaked, deeply splitting into 2 long teeth at orifice.		36 C. sect. Pseudocypereae
+	Female glumes muticous or mucronate, rarely aristate; utricles eventually obliquely patent, rarely horizontally patent or downward reflexed, inflated trigonous or slightly so, medium to long beaked or very shortly beaked		(32)
32 (31)	Female glumes oblong-lanceolate or narrowly ovate, without mucro or awn; utricles inflated trigonous, membranous or subleathery, medium to long beaked.		37 C. sect. Physocarpae
+	Female glumes ovate or broadly ovate, mucronate, rarely aristate; utricles slightly inflated trigonous, leathery or suberose, very shortly beaked.		38 C. sect. Paludosae
33 (28)	Female glumes dark purple-red or brown; utricles compressed trigonous, rarely trigonous		(34)
+	Female glumes pale, rarely dark brown; utricles trigonous or inflated trigonous (subplano-convex in C. sect. Secalinae)		(35)
34 (33)	Spikes numerous, bisexual, androgynous, usually several spikes borne in an involucral bract sheath.		26 C. sect. Decorae
+	Spikes 2-7, unisexual, solitary in an involucral bract sheath, terminal spikes male, rarely gynaecandrous, lateral spikes female.		27 C. sect. Aulocystis
35 (33)	Culms lateral, rarely central; nutlets usually constricted or with constriction on angles, rarely not constricted or without constriction; style base thickened or inflated, rarely not thickened		(36)
+	Culms central; nutlets not constricted or without constrictions on angles; style base not thickened		(37)
36 (35)	Female spikes densely many flowered; nutlets usually constricted or with constriction on angles, rarely not constricted.		34 C. sect. Rhomboidales
+	Female spikes sparsely several flowered; nutlets not constricted on angles.		35 C. sect. Careyanae
37 (35)	Male spikes 1-3, borne at apex of culm; utricles leathery, subplano-convex.		33 C. sect. Secalinae
+	Terminal spike male, rarely androgynous or gynaecandrous; utricles membranous or papery, rarely subleathery		(38)
38 (37)	Female spikes densely many flowered; involucral bracts usually without sheaths or with very short sheath; utricles eventually divaricate, horizontally patent, or downward reflexed, rarely obliquely patent, distinctly several veined		(39)
+	Female spikes usually sparsely flowered (densely flowered in C. sect. Hymenochlaenae); involucral bracts sheathed; utricles erect or slightly obliquely patent, greenish or greenish yellow, obscurely veined		(40)
39 (38)	Female glumes long aristate, rarely mucronate (C. ischnostachya and C. subtumida without mucro or awn); utricles eventually horizontally patent or slightly downward reflexed, rarely slightly divaricate, brown- green or dark brown or black-brown at maturity.		31 C. sect. Confertiflorae
+	Female glumes mucronate or muticous, rarely aristate; utricles eventually obliquely patent, rarely horizontally patent, yellowish green or stramineous, rarely brownish yellow.		32 C. sect. Molliculae
40 (38)	Female spikes oblong or shortly cylindric; utricles less than 3 mm.		28 C. sect. Chlorostachyae
+	Female spikes cylindric, narrowly cylindric, or linear- cylindric; utricles 4-7 mm, rarely 3-3.5 mm		(41)
41 (40)	Female spikes cylindric, rather densely flowered; utricles elliptic or obovate- elliptic, shortly 2-toothed at orifice.		29 C. sect. Hymenochlaenae
+	Female spikes narrowly cylindric or linear- cylindric, sparsely or very loosely flowered; utricles oblong-lanceolate, lanceolate, or narrowly oblong, obliquely truncate or very shortly 2-toothed at orifice.		30 C. sect. Debiles