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| 1 Leaf blades 20-60 mm wide, without a midrib (with 40-100 parallel nerves all of equal prominence), leathery, the apex obtuse; leaf margin scarious, minutely crisped-ruffled (feeling scaberulous to the touch) |
| 1 Leaf blades 0.5-25 (-52) mm wide, with a midrib, herbaceous, the apex acute; leaf margin various (smooth or scabrous, but not as described below). |
| ..2 Spike entirely staminate. |
| ....3 Culms distinctly red or purple at the base |
| ....3 Culms yellow to brown or black, without red or purple coloration. |
| ......4 Culms shorter than the leaves; widest leaf blades > 2 mm wide |
| ......4 Culms longer than the leaves; widest leaf blades < 2 mm wide |
| ..2 Spike pistillate or with both pistillate and staminate flowers. |
| ........5 Stigmas 2; achenes lenticular. |
| ..........6 Perigynia very obscurely or not at all serrulate, plump; plants slender rhizomatous |
| ..........6 Perigynia minutely but strongly and regularly serrulate on apical portion and beak, ± flattened; plants cespitose |
| ........5 Stigmas 3; achenes trigonous. |
| ............ 7 Perigynia pubescent near the tip |
| ............ 7 Perigynia glabrous. |
| ............ ..8 Spikes gynecandrous; beak of perigynium with apical teeth > 0.3 mm long |
| ............ ..8 Spikes androgynous or entirely pistillate; beak of perigynium with apex entire, emarginate, or with teeth < 0.2 mm long. |
| ............ ....9 Lower pistillate scales > 10 mm long |
| ............ ....9 Lower pistillate scales < 10 mm long. |
| ............ ......10 Perigynium beak > 2 mm long, as long as or longer than the perigynium body |
| ............ ......10 Perigynium beak < 2 mm long, or if more, then tapering to the perigynium body and shorter than the body. |
| ............ ........11 Perigynia > 4× as long as wide |
| ............ ........11 Perigynia < 4× as long as wide. |
| ............ ..........12 Perigynia 1-3, each with 2 marginal veins only |
| ............ ..........12 Perigynia 2-13, each lightly many-veined on the body in addition to 2 marginal veins |