1Stigmas 3 and nut trigonous, or, when stigmas 2 and nut lenticular (plano-convex or biconvex) some or all of the spikelets peduncled or terminal spikelet ♂. Spikelets either dissimilar in appearance (the terminal one ♂ and some or all the lateral ones ♀), or similar in appearance (all bisexual). Base of the peduncles of the lateral spikelets or of the branches of the inflorescence surrounded by a utriculiform or ocreiform bracteole (cladoprophyllum); inflorescence sometimes reduced to a single terminal spikelet
1'Stigmas 2 and nut lenticular. Spikelets similar in appearance, bisexual, sessile. Cladoprophylla usually absent
2Stigmas 3; nut trigonous.
2'Stigmas 2; nut lenticular (plano-convex or biconvex).
3Inflorescence consisting of more than one spikelet.
3'Inflorescence consisting of a single terminal spikelet.
4Lateral spikelets arising from a gaping, utriculiform, fertile (i.e. nut-bearing) cladoprophyll. Spikelets androgynous, up to 15 mm long. Bracts not sheathing. Stems 3-20 cm tall. Sp. 12
4'Lateral spikelets arising from a sterile cladoprophyll, or sessile without cladoprophyll.
5Stems scapiform, surrounded at the base by spadiceous sheaths in place of leaves. Leaves wide, conduplicate-petioled below. Secondary panicles contracted, very dense. Utricles with very long linear beak and very oblique mouth. Sp. 14
6Spikelets peduncled, in fascicles in the axils of at least some of the sheathing bracts, all androgynous or some wholly ♂ or ♀. Utricles long-beaked. Spp. 17-20
6'The peduncled or sessile spikelets or secondary panicles single or binate in the axils of the bracts.
7Spikelets similar in appearance, androgynous (upper flowers ♂, lower ones ♀).
7'Spikelets dissimilar in appearance, unisexual (or rarely gynaecandrous), the terminal one or some upper ones ♂, the remainder ♀ (occasionally the ♀ spikelets may have a few ♂ flowers, and the ♂ spikelets a few ♀ flowers). Or most of the spikelets shortly cylindrical, the ♂ spikelets lateral, 1-5 just below some of the terminal ♀ spikelets.
8Lower bracts not or only shortly (some millimeters) sheathing.
8'Lower bracts long sheathing.
9Apex of nut truncate, 0.5-0.75 mm ø, hollowed out. Style centred in the apical hollow of the nut. Utricles lageniform or rhomboid-lageniform. Spp. 27-30.
9'Apex of nut not truncate. Style base pyramidally thickened, often broader than apex of nut. Spp. 35-38
10Flowering stems arising from the axils of the leaves which are crowded on a short stem and much longer than the flowering stems. Style flexuous. Nut with irregularly excavated sides, seated on a spongy, disk-like stipe. Sp. 26
10'Flowering stems arising either from the centre of the leaves, or from lateral shoots bearing a few short-bladed leaves.
11Spikelets small, up to 15(-20) mm long.
11'Spikelets longer.
12Stems central. Spikelets numerous, ovoid or oblong-ovoid, arranged in often diffuse, compound panicles. Bracts long. Spp. 1-11
12'Stems lateral. Spikelets few, globose-ovoid, in a simple panicle. Bracts shorter than 8 cm, the sheaths not included. Sp. 21
13Utricles densely many-nerved. Spikelets 1-8(-14).
13'Utricles distinctly but not densely nerved. Leaves with reddish sheaths splitting into fibres. Spikelets 6-numerous. Spp. 15-16
14Utricles ellipsoid, short-beaked, more or less ciliate on the margins, spongy-thickened at the base. Spikelets 1-3(-4). Spp. 35-38
14'Utricles narrowly ellipsoid, long-beaked, more or less hispidulous on the faces, not spongy-thickened at the base. Spikelets 2-8(-14). Spp. 17-20.
15Leaves not crowded in a basal rosette but inserted all over the stem, the upper ones merging into leafy bracts, the lower ones gradually decreasing in length and merging into bladeless sheaths.
15'Leaves crowded at the base of the stem, often also some higher on the stem.
16Inflorescence a compound panicle consisting of 5-8 secondary panicles each containing numerous ♀ spikelets and 1-5 ♂ spikelets. Spikelets small, 4-8 mm long. Utricles glabrous, with short, ¼ mm long beak. Leaves sparsely hairy beneath., Sp. 13
16'Inflorescence simple, racemose, consisting of 4-9 spikelets; terminal spikelet ♂ (sometimes a second, smaller one added), remaining spikelets ♀, 1.5-4 cm long. Utricles densely hispid, with distinct, c. 1 mm long beak. Leaves glabrous. Sp. 50
17Nut excavated in the middle, the apex abruptly narrowed into a conspicuous, hastiform, i.e. cylindric, 1/2-1/3 mm long beak expanding into the annulate apex. Spp. 22-25
17'Nut without hastiform beak.
18Apex of nut truncate, ¾-1 mm wide, hollowed out. Style centred in the apical hollow of the nut. Utricles lageniform or rhomboid-lageniform. Spp. 27-30
18'Apex of nut not truncate, at most 0.5 mm wide.
19Nut mitrate, i.e. contracted at the apex and then expanded into a discoid annulus. Utricles ovoid or ellipsoid. Spp. 31-34
19'Nut not mitrate.
20Utricles densely papillose, erostrate or but shortly beaked. Sp. 39
20'Utricles not papillose, distinctly beaked.
21♀ Spikelets broadly ovoid or subglobose, with few narrowly lanceolate, c. 1 cm or more long utricles. Bracts sheathing. Rhizome short. Sp. 48.
21'♀ Spikelets not broadly ovoid-subglobose. Utricles smaller.
22Spikelets linear-cylindric, loosely flowered. Utricles nerveless (except for 2 submarginal nerves) or obscurely nerved, with long beak and oblique mouth. Bracts sheathing.
22'Spikelets oblong or cylindric. Utricles many-nerved.
23Utricles hispidulous, brownish. Sp. 46
23'Utricles glabrous, light green. Sp. 47
24Spikelets short-cylindric, few-flowered. Utricles fusiform-ellipsoid or rhomboid, at least towards the base many-nerved. Flowering stems lateral or central. Spp. 22-25
24'Spikelets cylindric, densely many-flowered.
25Utricles firm, of thick texture, short-beaked. Rhizome emitting strong stolons. Leaves conspicuously septate-nodulose. Spikelets erect. Bracts not or scarcely sheathing. Sp. 60
25'Utricles membranous, with long beak (except in C. brownii subsp. brownii).
26Spikelets erect. Utricles patulous, subinflated, many-nerved, with shortly bidentate beak. Style straight. Rhizome often creeping. Spp. 42-45.
26'Lower spikelets cernuous. Utricles widely patent to reflexed, closely many-ribbed, with bifurcate beak. Style flexuous. Rhizome cespitose. Sp. 49
27Utricles with whitish pubescent margins or hispidulous, densely and strongly many-nerved, 4-10 mm long. Spp. 35-38
27'Utricles glabrous, 1.5-5 mm long.
28Utricles rather large (4.5-5 mm long), with slender, linear, bidentate beak. Sp. 41
28'Utricles small (1.5-4 mm long), with short, subentire or slightly emarginate beak. Sp. 40
29Bracts sheathing. Spikelets often in fascicles. Utricles often hispidulous, membranous, nerved, usually long-beaked. Stigmas often very long. Spp. 56-59
29'Bracts not sheathing (or very shortly).
30Lateral spikelets sessile or the lowest shortly peduncled, erect. Terminal spikelet Glumes muticous. Sp. 55
30'Spikelets peduncled, cernuous. Glumes often awned.
31Spikelets 3-8, single at the nodes, cylindric, short peduncled. Terminal spikelet ♂ or (often with exception of basal spikelets) spikelets gynaecandrous. Spp. 52-54.
31'Spikelets 6-50, single or binate at the nodes, the lower ones long-peduncled, all androgynous or some ♂, linear-cylindric. Sp. 51
32Spikelets androgynous (upper flowers ♂, lower ones ♀).
32'Spikelets gynaecandrous (upper flowers ♀, lower ones ♂) Utricles membranous.
33Rhizome long-creeping. Spikelets 4-7. Utricles coriaceous, plano-convex, sharp-edged but not winged. Sp. 61
33'Rhizome short, forming dense tufts. Spikelets numerous or very numerous.
34Utricles coriaceous, with rounded margins. Bracts inconspicuous. Sp. 62
34'Utricles membranous, with acute or winged margins. Lower bracts foliaceous. Sp. 63
35Utricles with rounded margins, densely whitish-puncticulate, beakless or very shortly beaked. Spikelets ebracteate (bracts glumiform). Sp. 66
35'Utricles with acute or winged margins, not puncticulate.
36Utricles obliquely erect, also when mature. Spikelets more or less distinctly bracteate. Sp. 65.
36'Utricles widely spreading or reflexed when mature. Spikelets not or inconspicuously bracteate (bracts glumiform). Sp. 64