1Spikelets very small, 2-3 mm long. Glumes 2 mm long. Nut 1½-1¾ mm long. All the leaves usually much reduced, the basal ones bladeless, the cauline ones with a very short blade 1-2(-5) cm long.
1'Spikelets, glumes, and nuts larger. At least part of the leaves with well-developed much longer blades.
2Leaves sword-shaped, very flat with sharp edges, equitant. Stems ancipitous.
2'Leaves terete, or biconvex with obtuse edges. Stems terete or somewhat compressed, not ancipitous.
3Stems and leaf-sheaths (often also the leaf-blades) asperous.
3'Stems and leaves smooth.
4Spikelets in clusters of 3-5. Glumes acute to mucronulate. Nut proper ellipsoid, c. 2 mm long, suddenly contracted into the densely sericeous c. 1½ mm long style-base.
4'Most spikelets solitary, some of them in clusters of 2-3. Glumes acutish, muticous. Nut ovoid, gradually passing into the hispid, dark brown to blackish style-base, c. 3 mm long.
5Perianth consisting of (3-)6 bristles c. 2 mm long. Anthers with very shortly produced connective. Inflorescence stiffly erect
5'Perianth absent (rarely a single very short bristle present). Anthers with distinctly produced connective.
6Branches of the inflorescence drooping. Filaments strongly elongated after anthesis, (1-)2-2½ cm long, comose
6'Branches of the inflorescence erect. Filaments shorter, only moderately elongated after anthesis, never comose.
7Leaves densely ciliate on the edges, narrow, 3-5(-7) mm wide. Stems low, 30-50 cm tall.
7'Leaves glabrous, usually broader. Stems usually taller.
8Nut at the base narrowed into a 3-winged stipe, triquetrous. Persistent style-base glabrous or more or less hispid, never densely sericeous
8'Nut sessile, obtusely trigonous to subterete. Persistent style-base densely sericeous.
9Lower bracts very shortly laminate. Nut gradually tapering into shortly pyramidal persistent style-base
9'Lower bracts long, similar to the leaves. Nut abruptly narrowed into c. 1½ mm long persistent style-base.
10Glumes ovate-lanceolate, acute, the longest c. 5 mm. Spikelets 1-flowered, 5-6 mm long, in turbinate clusters. Nut ovoid-ellipsoid, 3½-4 by 1-1⅓ mm.
10'Glumes ovate, obtuse, up to 4 mm long. Spikelets (1-)2-3-flowered, 3-4 mm long, in ovoid to globose clusters. Nut broadly ovoid or subglobose, 3-3½ by 1½ mm.
11Leaves prominently transversely septate. Nut with thickened suberous angles.
11'Leaves not septate, pithy within, the pith almost continuous, not divided into remote distinct septa.
12Stem leafless. Spikelets 1-flowered
12'Stem with 1-2 short leaves. Spikelets 2-3-flowered.
13Nut ellipsoid to oblong-ellipsoid, 3-5 by 1½-2 mm, smooth and shining. Glumes muticous.
13'Nut obovoid or ellipsoid, 1½-2 by 1-1¼ mm, strongly rugulose by many much raised irregular ridges, opaque. Glumes usually mucronulate