1 (1)	Inflorescence a large compound anthelodium; distal partial nflorescences cylindrical, twice as long as wide or more, to 50 mm long (excl. peduncle), 10-30 mm wide, with (30)40-100 spikes.		(1)
+	Inflorescence a multiple spike or small anthelodium; distal partial inflorescences ovoid or obovoid, to 10-25 x 3-30 mm, if much longer than wide, then c. 3-5 mm wide (C. iria and C. alulatus), with 3-30(40) spikes.		(2)
2 (2)	+ Stigmas 3.		(2)
+	Stigmas 2 (or partly 3).		4 C. alopecuroides
3	Spikes but slightly compressed, subterete, at right angles to rachis when ripe; glumes muticous or apiculate.		2 C. digitatus
+	Spikes distinctly compressed, from suberect to spreading at right angles from rachis when ripe; glumes with short but distinct mucro.		(4)
4 (3)	Distal partial inflorescences sessile or peduncle very short; spikes suberect, completely hiding rachis of partial inflorescence.		5 C. imbricatus
+	Peduncles of distal partial inflorescences to 50 mm; spikes obliquely patent to almost at right angles to rachis, the latter therefore visible.		(5)
5 (4)	Spikes less crowded and leaving rachis visible; glumes brown with nerves on sides.		3 C. exaltatus
+	Spikes crowded, rachis hardly visible between; glumes yellow or light brown, sides nerveless.		1 C. dives
6 (6)	Robust plants; basal leaf-blades reduced, practically absent or few and short.		(6)
+	Smaller plants; leaf-blades well-developed, long .		(7)
7 (6)	Culm terete, septate.		6 C. articulatus
+	Culm trigonous, at least, in distal part, not or obscurely sepatate.		(8)
8 (7)	Culm distinctly trigonous to base, sides concave; spike axis hardly winged.		9 C. malaccensis
+	Culm distally obtusely trigonous; spike rachis widely winged.		(9)
9 (8)	Rhizome short, culm not septate; spike rachis with reddish wings.		8 C. pangorei
+	Rhizome long, stoloniferous, culm sometimes obscurely septate; spike rachis with hyaline, colourless wings.		7 C. corymbosus
10 (10)	Distal partial inflorescences compact, globose or ellipsoid groups of spikes (rachis not visible); spikes 1-1.5 mm wide.		(10)
+	Distal partial inflorescences not compact; with spikes diffusely arranged (rachis visible), or if sometimes. rather compact, then spikes 2-2.5 mm wide (C. glaber).		(11)
11 (10)	Inflorescence greenish; primary rays several, to more than 20 cm long, rigidly suberect.		15 C. nutans
+	Inflorescence brown; primary rays few, up to 7 cm long.		16 C. glomeratus
12 (12)	Annuals, roots fibrous.		(12)
+	Stoloniferous perennials.		(13)
13 (13)	Glumes 1-2 mm, apex widely rounded; keel incurved, obtuse; sides nerveless, hyaline.		(13)
+	Glumes 2-4 mm, apex narrow; keel straight or recurved, obtuse or mucronate; only margins nerveless, scarious, not hyaline.		(14)
14 (13)	Spikes finally reflexed; glumes 1.5-2 mm.		17 C. alulatus
+	Spikes suberect; glumes 1-1.5 mm.		18 C. iria
15	Spikes 8-20 x c. 3.5 mm, with to 40 flowers, strongly compressed.		19 C. compressus
+	Spikes 7-9 x 2.5-3 mm, with 8-14 flowers, not strongly compressed.		20 C. glaber
16	Flowers distigmatic.		21 C. serotinus
+	Flowers tristigmatic.		(17)
17 (16)	Inflorescence with 2 or more foliose involucral bracts separated by distict internode; leafblades 1.5-3 mm wide, very long attenuate; stolons thin (less than 0.5 mm, resembling roots), white, short-lived, ending to black bulbil.		10 C. bulbosus
+	No distinct internodes between involucral bracts; leafblades mostly more than 3 mm wide; stolons c. 1 mm diam. or more, not ending with black bulbil.		(18)
18 (17)	Stolons rather soft, white, c. 1 mm diam. (thicker than roots), ending with globose, whitish tuber; glumes yellow or light brown, sides with 3-4 long, distinct nerves.		11 C. esculentus
+	Stolons strong, ligneous; glumes brown to reddish or blackish brown, sides not with 3-4 distinct nerves.		(19)
19 (19)	Inflorescence an anthelodium, with up to 70 mm long, not rigidly suberect primary rays; spikes in distal partial inflorescence mostly distinctly pikately arranged, spreading, subterete or terete; stolons long, producing rooting tubers.		(19)
+	Inflorescence an anthelodium, with up to 15 cm long, rigid, suberect primary rays; spikes in distal partial inflorescences nearly digitately together, suberect, compressed; stolons short, without tubers.		14 C. longus
20	Stolons up to 3 mm diam.; involucral bracts 1.5-2 mm wide, primary rays few, to 25 mm; spikes turgid, terete; glumes closely imbricating.		13 C. stoloniferus
+	Stolons up to 2 mm diam.; involucral bracts to 6 mm wide, primary rays to 60 mm; spikes not turgid, subterete; glumes not closely imbricating.		12 C. rotundus