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| 1 Apex of perigynium beak terminated by 2 teeth, mostly > 0.5 mm long. |
| ..2 Perigynia > 4× as long as wide (8-15 × 1-3 mm). |
| ....3 Apical teeth of perigynium beak erect; achenes oblong-obovoid or obovoid; at least proximal pistillate scales with 3-5 (-7)-veined center |
| ....3 Apical teeth of perigynium beak reflexed; achenes elongate; pistillate scales with 1-veined center |
| ..2 Perigynia < 4× as long as wide. |
| ......4 Perigynia > (9-) 10 mm long. |
| ........5 Sheaths, at least the proximal sheath fronts, densely tomentose at mouth; apical teeth of perigynium beak often > 1 mm long |
| ........5 Sheaths glabrous; apical teeth of perigynium beak not more than 1 mm. |
| ..........6 Perigynia 7-11-, 5-12-, or 12-25-veined |
| ..........6 Perigynia 12-34-veined. |
| ............ 7 Basal and proximal leaf sheaths reddish or purplish |
| ............ 7 Basal and proximal leaf sheaths yellowish to brown, without trace of red or purple |
| ......4 Perigynia < 10 mm long. |
| ............ ..8 At least proximal pistillate scales with long, rough awn. |
| ............ ....9 Perigynia with 2 strong marginal veins, otherwise veinless or veined only proximally; leaves not septate-nodulose. |
| ............ ....9 Perigynia with 5+ strong veins extending length of bodies; leaves septate-nodulose. |
| ............ ......10 Perigynium beak with apical teeth (0.4-) 0.6-3 mm long, often > 1 mm long |
| ............ ......10 Perigynium beak with apical teeth < 1 mm long. |
| ............ ........11 Perigynium body obovoid, widest distally; proximal bract > 3× as long as the inflorescence |
| ............ ........11 Perigynium body ovoid or lanceoloid or ellipsoid, widest at middle or proximally; proximal bract usually < 2× as long as the inflorescence. |
| ............ ..........12 Perigynium beak 0.9-1.7 mm long; mature perigynia dull |
| ............ ..........12 Perigynium beak 0.2-6 mm long; mature perigynia somewhat glossy |
| ............ ..8 All pistillate scales obtuse to acuminate or cuspidate. |
| ............ ............ 13 Culms with some red or purple at base. |
| ............ ............ ..14 All perigynia erect or ascending; leaves not septate-nodulose |
| ............ ............ ..14 At least proximal perigynia in each spike spreading or reflexed; leaves sparsely septate-nodulose |
| ............ ............ 13 Culms brown or black at base, without trace of red or purple. |
| ............ ............ ....15 Pistillate scales with 5-7-veined center |
| ............ ............ ....15 Pistillate scales with 1-3-veined center. |
| ............ ............ ......16 Leaves not septate-nodulose |
| ............ ............ ......16 Leaves at least sparingly septate-nodulose |
| 1 Apex of perigynium beak entire, emarginate, or with teeth mostly < 0.5 mm long. |
| ............ ............ ........17 Leaf blades variously hairy. |
| ............ ............ ..........18 Plant brown or black at base |
| ............ ............ ..........18 Plant with at least some red or purple at base |
| ............ ............ ........17 Leaf blades glabrous. |
| ............ ............ ............ 19 Bracts without blades. |
| ............ ............ ............ ..20 Leaves < 1 mm wide |
| ............ ............ ............ ..20 Leaves much wider, often over 10 mm wide |
| ............ ............ ............ 19 Bracts, at least the proximal, with distinct blade. |
| ............ ............ ............ ....21 Young leaves V-shaped or rounded in cross section, adaxial surface without 2 marginal veins more prominent than midvein or other veins. |
| ............ ............ ............ ......22 Perigynium beak with 2 distinct terminal teeth, usually > 0.2 mm long. |
| ............ ............ ............ ........23 At least proximal pistillate scales awned, awn at least 1/2 as long as body; leaves conspicuously septate-nodulose. |
| ............ ............ ............ ..........24 Base of culm strongly red or purple; leaves 2-4 mm wide |
| ............ ............ ............ ..........24 Base of culm brown, without or with only trace of red or purple; leaves 4–15 mm wide. |
| ............ ............ ............ ............ 25 Distal pistillate scales acute, acuminate, or short-awned, awn less than 1/2 length of body |
| ............ ............ ............ ............ 25 Distal pistillate scales with awn at least about as long as body |
| ............ ............ ............ ........23 Pistillate scales obtuse to acuminate, sometimes very shortly awned; leaves not or only weakly septate-nodulose. |
| ............ ............ ............ ............ ..26 Plants with long-creeping rhizomes; leaves usually not septate-nodulose |
| ............ ............ ............ ............ ..26 Plants with short-ascending rhizomes; leaves at least sparingly septate-nodulose. |
| ............ ............ ............ ............ ....27 Proximal perigynia in each spike ascending or spreading-ascending |
| ............ ............ ............ ............ ....27 Proximal perigynia in each spike spreading or reflexed |
| ............ ............ ............ ......22 Perigynium beak entire, emarginate, or with 2 apical teeth < 0.2 mm long. |
| ............ ............ ............ ............ ......28 Perigynia rounded at base, sides proximally distinctly convex. |
| ............ ............ ............ ............ ........29 Perigynia with veins slightly prominent |
| ............ ............ ............ ............ ........29 Perigynia with veins slightly impressed |
| ............ ............ ............ ............ ......28 Perigynia tapering at base, sides straight or only slightly convex proximally. |
| ............ ............ ............ ............ ..........30 Perigynia rounded at apex, beakless or with beak < 0.3 mm long. |
| ............ ............ ............ ............ ............ 31 Widest leaf blades < 5 mm wide; plants usually not cespitose |
| ............ ............ ............ ............ ............ 31 Widest leaf blades usually > 5 mm wide; plants usually cespitose |
| ............ ............ ............ ............ ..........30 Perigynia tapering to beak at least > (0.3-) 0.5 mm long. |
| ............ ............ ............ ............ ............ ..32 Proximal perigynia in each spike spreading at right angles or reflexed at maturity; leaves and sheaths sparsely septate- nodulose |
| ............ ............ ............ ............ ............ ..32 Proximal perigynia in each spike ascending or spreading-ascending; leaves and sheaths not septate-nodulose. |
| ............ ............ ............ ............ ............ ....33 Plants usually colonial; perigynia and leaves often papillose |
| ............ ............ ............ ............ ............ ....33 Plants cespitose; perigynia and leaves not papillose |
| ............ ............ ............ ....21 Leaf blades M-shaped in cross section when young, adaxial surface with 2 marginal veins more prominent than midvein and other marginal veins, sometimes apparent only on proximal leaves and on proximal part of blade. |
| ............ ............ ............ ............ ............ ......34 Perigynium beakless or with beak < 0.5 mm long, entire or with 2 apical teeth < 0.1 mm long. |
| ............ ............ ............ ............ ............ ........35 Widest leaf blades (usually basal) > 10 mm wide. |
| ............ ............ ............ ............ ............ ..........36 Distal pistillate spikes strongly pendulous, perigynia > 100 per spike; [exotic] |
| ............ ............ ............ ............ ............ ..........36 Distal pistillate spikes erect, perigynia < 30 per spike; [native]. |
| ............ ............ ............ ............ ............ ............ 37 Perigynia trigonous with rounded angles in cross section |
| ............ ............ ............ ............ ............ ............ 37 Perigynia sharply trigonous in cross section |
| ............ ............ ............ ............ ............ ........35 Widest leaf blades < 10 mm wide.
not more than 10 mm wide. |
| ............ ............ ............ ............ ............ ............ ..38 Perigynia not prominently veined, veins somewhat impressed |
| ............ ............ ............ ............ ............ ............ ..38 Perigynia at least slightly prominently veined or veinless except for 2 marginal veins. |
| ............ ............ ............ ............ ............ ............ ....39 Perigynia rounded at base, sides proximally convex |
| ............ ............ ............ ............ ............ ............ ....39 Perigynia tapering at base, sides proximally straight, concave or slightly convex. |
| ............ ............ ............ ............ ............ ............ ......40 Perigynia transversely wrinkled; leaf sheaths sparsely septate-nodulose |
| ............ ............ ............ ............ ............ ............ ......40 Perigynia not transversely wrinkled; leaf sheaths not septate-nodulose. |
| ............ ............ ............ ............ ............ ............ ........41 Perigynia sharply trigonous in cross section |
| ............ ............ ............ ............ ............ ............ ........41 Perigynia terete or with rounded angles in cross section. |
| ............ ............ ............ ............ ............ ............ ..........42 Perigynia with 2 marginal veins and not more than 10 veins on faces |
| ............ ............ ............ ............ ............ ............ ..........42 Perigynia with more than 12 veins. |
| ............ ............ ............ ............ ............ ............ ............ 43 Plants usually colonial, not cespitose; perigynia papillose at least faintly. |
| ............ ............ ............ ............ ............ ............ ............ 43 Plants usually cespitose; perigynia not papillose. |
| ............ ............ ............ ............ ............ ......34 Perigynium with distinct beak > 0.5 mm, usually with apical teeth > 0.1 mm long. |
| ............ ............ ............ ............ ............ ............ ............ ..44 Perigynia with 2 distinct marginal veins, otherwise veinless or with very weak veins proximally. |
| ............ ............ ............ ............ ............ ............ ............ ....45 Perigynium beak entire, emarginate, or with apical teeth < 0.1 mm long |
| ............ ............ ............ ............ ............ ............ ............ ....45 Perigynium beak with apical teeth 0.2-1 mm. |
| ............ ............ ............ ............ ............ ............ ............ ......46 Perigynium beak usually < 1 mm long. |
| ............ ............ ............ ............ ............ ............ ............ ......46 Perigynium beak sometimes > 2 mm long |
| ............ ............ ............ ............ ............ ............ ............ ..44 Perigynia with more than 2 veins extending most of length of bodies. |
| ............ ............ ............ ............ ............ ............ ............ ........47 Pistillate scales with narrow, indistinct bodies, scarcely enlarged at bases |
| ............ ............ ............ ............ ............ ............ ............ ........47 Pistillate scales with wide, flat bodies, sometimes terminating in awns. |
| ............ ............ ............ ............ ............ ............ ............ ..........48 Perigynium beak entire or emarginate. |
| ............ ............ ............ ............ ............ ............ ............ ............ 49 Perigynium with not more than 5 veins extending length of body on abaxial face, veinless or weakly veined on adaxial face |
| ............ ............ ............ ............ ............ ............ ............ ............ 49 Perigynium with > 8 equally prominent veins on both faces. |
| ............ ............ ............ ............ ............ ............ ............ ............ ..50 Perigynia bluntly angled in cross section |
| ............ ............ ............ ............ ............ ............ ............ ............ ..50 Perigynia sharply angled in cross section |
| ............ ............ ............ ............ ............ ............ ............ ..........48 Perigynium beak with 2 distinct teeth at apex, usually > 0.2 mm long. |
| ............ ............ ............ ............ ............ ............ ............ ............ ....51 Pistillate spikes, at least the proximal, lax, proximal and middle perigynia separated by internodes at least 1/4 their length; leaves and sheaths not septate-nodulose |
| ............ ............ ............ ............ ............ ............ ............ ............ ....51 Pistillate spikes dense, proximal and middle perigynia separated by internodes less than 1/10 their length; proximal leaves and sheaths sparingly septate-nodulose. |
| ............ ............ ............ ............ ............ ............ ............ ............ ......52 Pistillate scales, at least proximal, awned, awn at least 1/4 of scale body length. |
| ............ ............ ............ ............ ............ ............ ............ ............ ........53 Distal pistillate scales acuminate or with awn less than 1/2 body length; staminate spikes usually 2+ |
| ............ ............ ............ ............ ............ ............ ............ ............ ........53 Distal pistillate scales awned, awn usually more than 1/2 body length; staminate spikes 1, sometimes with 1 much smaller spike laterally |
| ............ ............ ............ ............ ............ ............ ............ ............ ......52 Pistillate scales obtuse to acute or apiculate, apiculus not more than 1/10 of body length. |
| ............ ............ ............ ............ ............ ............ ............ ............ ..........54 Culms purple-red at base; achenes with style persistent |
| ............ ............ ............ ............ ............ ............ ............ ............ ..........54 Culms brown at base, without trace of red or purple; achenes with style deciduous |