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| 1 Apex of perigynium beak with 2 teeth at least (0.4-) 0.5 mm long. |
| ..2 Perigynia with 2 distinct marginal veins, otherwise veinless or only very faintly veined; leaves not septate-nodulose |
| ..2 Perigynia with 5+ distinct veins; at least proximal leaves septate-nodulose, rarely not. |
| ....3 Perigynia with serrulate wing on margins; spikes usually 20+, sessile, pistillate or androgynous and similar in appearance, forming a dense, ovoid or oblong head, rarely with proximal spike separated |
| ....3 Perigynia without wing on margins; spikes not more than 10, usually at least proximal shortly pedunculate, sometimes subsessile, distal and proximal spikes usually dissimilar in appearance, usually not crowded into a dense head. |
| ......4 Pistillate scales obtuse to acuminate, awnless or at most with a rough apiculus. |
| ........5 Staminate spike usually 1; perigynia 15-20-veined, each 10-20 mm long |
| ........5 Staminate spikes usually 1-3+; perigynia 6-15 (-22)-veined, each 4-10 (-12.5) mm. |
| ..........6 Perigynia 6-14 (-15)-veined |
| ..........6 Perigynia 14-25-veined |
| ............ 7 Perigynia narrowly ovate to subglobose, 2-2.5× as long as wide |
| ............ 7 Perigynia elliptic to ovate, 3-4.5× as long as wide |
| ......4 Pistillate scales, at least some, with a scabrous awn. |
| ............ ..8 Perigynia (9-) 10+ mm long. |
| ............ ....9 Pistillate spikes cylindric, much longer than wide; staminate spikes (1-) 2-6 |
| ............ ....9 Pistillate spikes globose, ovoid, or cylindric, about as long as wide; staminate spikes usually 1 |
| ............ ..8 Perigynia < 9 mm long. |
| ............ ......10 Upper pistillate scales with awn > ½ as long as the body |
| ............ ......10 Upper pistillate scales acute to short-awned, awn < ½ as long as the body. |
| ............ ........11 Beak of perigynia with teeth 1.1-3 mm long |
| ............ ........11 Beak of perigynia with teeth often < 1 mm long. |
| ............ ..........12 Staminate spikes 1 (-4); perigynium beak > 1.7 mm long |
| ............ ..........12 Staminate spikes 1-6; perigynium beak often < 1.7 mm long. |
| ............ ............ 13 Perigynia veined only at base; widest leaves < 4 mm wide |
| ............ ............ 13 Perigynium veined to tip of body and often into beak; widest leaves mostly > 4 mm wide. |
| ............ ............ ..14 Pistillate scales with margins serrulate distally; awn, when present, rough. |
| ............ ............ ....15 Perigynia 3.1-4.8 × 0.9-1.5 (-1.8) mm; staminate spikes 1-2 |
| ............ ............ ....15 Perigynia 2.5-8 × 1.2-3.5 mm; staminate spikes usually 3-7 |
| ............ ............ ..14 Pistillate scales with margins entire; awn, when present, usually smooth. |
| ............ ............ ......16 Perigynia 9-15-veined |
| ............ ............ ......16 Perigynia 14–25-veined. |
| ............ ............ ........17 Perigynia narrowly ovate to subglobose, 2-2.5× as long as wide |
| ............ ............ ........17 Perigynia elliptic to ovate, 3-4.5× as long as wide |
| 1 Apex of perigynium beak entire, emarginate, or with 2 teeth < 0.5 mm long. |
| ............ ............ ..........18 Perigynia minutely papillose, at least distally (at 20× magnification). |
| ............ ............ ............ 19 Some roots with yellow-brown felty covering |
| ............ ............ ............ 19 Roots brown or black, without yellow-brown felty covering, rarely with white felty covering. |
| ............ ............ ............ ..20 Leaf blades and/or sheaths pubescent, at least at junction of blade and sheath |
| ............ ............ ............ ..20 Leaf blades and sheaths glabrous. |
| ............ ............ ............ ....21 Terminal spike gynecandrous |
| ............ ............ ............ ....21 Terminal spike staminate or androgynous. |
| ............ ............ ............ ......22 Pistillate scales obtuse to acuminate or with awn < 1 mm long; staminate scales not awned |
| ............ ............ ............ ......22 Lower pistillate scales with awn 1.2-3.5 mm long; staminate scales awned |
| ............ ............ ..........18 Perigynia not papillose, essentially smooth. |
| ............ ............ ............ ........23 Terminal spike gynecandrous. |
| ............ ............ ............ ..........24 Perigynia with distinct beak 0.5-4 mm long. |
| ............ ............ ............ ............ 25 Larger spikes usually with > 50 perigynia; achenes 2-3 mm long |
| ............ ............ ............ ............ 25 Larger spikes with < 40 perigynia; achenes 1-2 mm long |
| ............ ............ ............ ..........24 Perigynia beakless or with beak < 0.5 mm long. |
| ............ ............ ............ ............ ..26 Adaxial side of leaves with 2 marginal veins more prominent than midvein; young leaves M-shaped in cross section. |
| ............ ............ ............ ............ ....27 Perigynia ovoid, usually > 1.5× as long as wide; apex tapered to beak; sheaths of proximal leaves not septate-nodulose |
| ............ ............ ............ ............ ....27 Perigynia subcircular, < 1.2× as long as wide; apex rounded, abruptly beaked; sheaths of proximal leaves septate-nodulose |
| ............ ............ ............ ............ ..26 Adaxial side of leaves without 2 marginal veins more prominent than midvein; young leaves V-shaped or rounded in cross section. |
| ............ ............ ............ ............ ......28 Leaf blades and/or sheaths pubescent, at least at junction of blade and sheath |
| ............ ............ ............ ............ ......28 Leaf blades and sheaths glabrous. |
| ............ ............ ............ ............ ........29 Perigynia erect or ascending |
| ............ ............ ............ ............ ........29 Perigynia ascending, spreading at about right angles, or reflexed when mature |
| ............ ............ ............ ........23 Terminal spike staminate or androgynous. |
| ............ ............ ............ ............ ..........30 Leaves and/or sheaths pubescent, at least at junction of blade and sheath. |
| ............ ............ ............ ............ ............ 31 Larger leaves 8-23 mm wide, only the sheaths pubescent |
| ............ ............ ............ ............ ............ 31 Leaves < 8 mm wide, blades and usually also the sheaths pubescent. |
| ............ ............ ............ ............ ............ ..32 Perigynium beak 0.5-3 mm long, often > 1 mm long, about 1/2 the length of the body; proximal pistillate scales awned |
| ............ ............ ............ ............ ............ ..32 Perigynium beak absent or not more than 0.5 (-0.7) mm long, not > 1/4 the length of the body; proximal pistillate scales acute, acuminate or cuspidate. |
| ............ ............ ............ ............ ..........30 Leaves and sheaths usually glabrous, rarely papillose. |
| ............ ............ ............ ............ ............ ....33 Style persistent on achene in fruit; larger leaves and sheaths usually at least sparsely septate-nodulose, rarely not. |
| ............ ............ ............ ............ ............ ......34 Perigynia (9-) 10+ mm long; staminate spike usually 1 |
| ............ ............ ............ ............ ............ ......34 Perigynia < 10 mm long; staminate spikes 1-5 (-7). |
| ............ ............ ............ ............ ............ ........35 Pistillate scales with margins serrulate distally, apex usually rough-awned. |
| ............ ............ ............ ............ ............ ..........36 Distal pistillate scales with apex acute to short-awned, awn < 1/2 as long as the body |
| ............ ............ ............ ............ ............ ..........36 Distal pistillate scales with apex long-awned, awn > 1/2 as long as the body |
| ............ ............ ............ ............ ............ ........35 Pistillate scales with margins entire, apex awnless or with short, smooth awn. |
| ............ ............ ............ ............ ............ ............ 37 Perigynia not inflated, thick walled, brownish, dull |
| ............ ............ ............ ............ ............ ............ 37 Perigynia slightly to strongly inflated, thin walled, yellowish to purplish, shiny |
| ............ ............ ............ ............ ............ ....33 Style deciduous; larger leaves and sheaths sometimes septate-nodulose, more often not. |
| ............ ............ ............ ............ ............ ............ ..38 Leaf blades, at least widest, M-shaped in cross section when young, adaxial surface with 2 marginal veins more prominent than midvein. |
| ............ ............ ............ ............ ............ ............ ....39 Widest leaf blades 8-23 mm wide, septate-nodulose |
| ............ ............ ............ ............ ............ ............ ....39 Widest leaf blades < 6 mm wide, not septate-nodulose. |
| ............ ............ ............ ............ ............ ............ ......40 Pistillate scales awned, longest awn > 0.5 mm long |
| ............ ............ ............ ............ ............ ............ ......40 Pistillate scales obtuse to acuminate or short-awned, awn < 0.2 mm long |
| ............ ............ ............ ............ ............ ............ ..38 Leaf blades V-shaped in cross section when young, adaxial surface without 2 marginal veins more prominent than midvein. |
| ............ ............ ............ ............ ............ ............ ........41 Proximal perigynia in each spike spreading at right angles or reflexed at maturity; leaf blades and sheaths sparsely septate-nodulose |
| ............ ............ ............ ............ ............ ............ ........41 Proximal perigynia in each spike ascending or spreading-ascending; leaf blades and sheaths not septate-nodulose. |
| ............ ............ ............ ............ ............ ............ ..........42 Plant base brown or blackish, without trace of red or purple |
| ............ ............ ............ ............ ............ ............ ..........42 Plant base red or purple tinged, sometimes only sparsely so. |
| ............ ............ ............ ............ ............ ............ ............ 43 Perigynia distinctly veined on faces; pistillate scales brown or black |
| ............ ............ ............ ............ ............ ............ ............ 43 Perigynia veinless or with veins only proximally; pistillate scales white-hyaline or red-brown |