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5Pistillatespike 3-4 mm in diameter, with ca. 2-3 vertical rows of perigynia; perigynia 2.5-3.5 mm long, 1.5-2.0 mm wide; leaves 2-4.5 mm wide, pale green
6Culms to 10 dm tall, (2-) 3-5 mm in diameter near base; larger leaves ca. 5 mm wide; plants forming large clumps; [plants of shallow soils on sloping rock outcrops]
6Culms to 5 dm tall, ca. 1-2 mm in diameter near the base; larger leaves ca. 2-4 mm wide; plants forming small, spaced clumps, interconnected by long-creeping rhizomes; [plants of mountain slopes in more-or-less deep soils]
1Inflorescence 7-15 cm long, the basal 3-9 branches well-separated from one another; perigynia broadly obovoid, 1.3-1.5× as long as wide; sheathsconcave at the mouth; leaves 3-8 mm wide; [of swamps of the Coastal Plain and lower Piedmont]
1Inflorescence 2-8 cm long, the basal 1-5 branches indistinct to slightly separated; perigyniaovoid to lance-ovoid, ca. 2× as long as wide; sheaths prolonged beyond the blade; leaves 1-3 mm wide; [of Mountain wetlands in VA (and TN?) and northward].
2 Inner band of leaf sheath strongly copper-colored (and also red-dotted); basal branches of inflorescence often weakly separated; perigynia nearly or completely concealed by the scales
(c) Marcum, Paul - CC-BY-NC, permission granted to NCBG
(c) Ward, Scott G - CC-BY
1Perigynium with (22-) 25-32 veins, all of which are conspicuous (the central one slightly more distinct); perigyniumbeak various; foliage various; bracts various.
(c) Wiegersma, Quinten - CC-BY
2Perigynium with a short, bent beak, usually abruptly bent to one side.
2Perigynium tapering to a straight or slightly curved beak (or a long, curved beak in C. radfordii) (note: some beaks may curve in pressing).
(c) Bradley, Keith
7Perigyniumbeaks long (to 1.5 mm long) and excurved; basalsheaths green, white, and brownish striped; [endemic to the escarpment gorge area near the SC-NC-GA tricorner]
7Perigyniumbeaks straight or slightly curved; basalsheaths either purple, wine-red, or brownish, not prominently green-and-white striped; [collectively widespread in our area].
(c) Ward, Scott G
(c) Ward, Scott G
8Basalsheaths purple or wine-red (may weather to brown in C. gracilescens).
15 Widest leaf on vegetative shoots (including overwintered leaves) 2.0-6.0 (-6.9) mm wide; medialpistillatespikes more loosely flowered, the ratio of the number of perigynia to spike length (measured in mm) (0.20-) mean 0.41 (-0.52)
15 Widest leaf on vegetative shoots (including overwintered leaves) 5.7-11.3 mm; medialpistillatespikes more densely flowered, the ratio of the number of perigynia to spike length (measured in mm) (0.47-) mean 0.57 (-0.90)
1 Primary culm solitary (i.e., lacking additional basalspikes originating from the same sheaths, excepting hybrids); however, some taxa may exhibit deceptively short individual culms (e.g., C. emmonsii, C. nigromarginata, C. reznicekii).
16Beak of perigynium (0.5-) 0.6-1.3 mm long; hairs at base of the beak and below densely short-retrorse only on both surfaces; [high elevations of the s. Appalachians]
10 Body of the perigyniumellipsoid, distinctly longer than wide; achene angles narrow to slightly rounded.
18 Plants with conspicuously long rhizomes, forming clonal patches; perigynia typically papillate; [collectively of the Coastal Plain and, less commonly, Piedmont].
18 Plants cespitose (sometimes loosely so from slender rhizomes in C. novae-angliae and C. peckii); perigyniapapillae not evident to rather conspicuous; [collectively widespread in our area].
23Culms usually variable in length, (4.5-) 6.6-38 (-51) cm tall; widest leaf (1.9-) 2.3-4.5 mm wide; at least some pistillatescales often with reddish to purplish/black color below the distal tip extending laterally from near the margin to the green or brown longitudinal mid-stripe on either side of midvein
23Culms subequal in length, height 1.9-9.9 (-13.7) cm tall, widest leaf 1.2-2.2 (-2.5) mm wide; any reddish color on pistillatescales below the distal tip not extending laterally from near the margin to the green or brown longitudinal mid-stripe on either side of midvein
22Achene body (0.9-) 1.2-1.3 (-1.5) mm long; fertile culms mostly 17-35 cm tall; pistillatescales 2.0-3.4 mm long.
24Scales of the median portion of the staminatespike with obtuseapices and with minute teeth rarely present on the midrib; staminatespike (7.8-) 8.0-12.5 (-13.5) mm long with peduncles mostly 1.0-6.0 mm; culms erect, subequal to the leaves; [mostly of loamy or clayey soils of the Piedmont and Mountains]
4Awn of pistillatescales 0.5-1.5 mm long; adaxial surface of perigynia lacking nerves; [prairies; s. IL, MO, se. KS, and OK south to AR and se. TX, and also introduced eastwards in disturbed sites]
1 Plants with short rhizomes, the culms therefore clumped; terminal and uppermost lateralspike usually overlapping.
(c) Ward, Scott G
3 Leaves green; longest bractblade of uppermost lateralspike 1.6-4.6 (-7.1) cm long; perigynia (1.6-) 1.9-3× as long as thick; [Coastal Plain; NC s. to FL, w. to MS]
9Pistillatescales green, hyaline, or pale tan; [native in our area (except C. austrina and C. muricata ssp. lamprocarpa), common and widespread in our area].
11Perigynia spreading, either nerved or nerveless on the upper (ventral) surface; scalesacuminate or with an awn to 1.5 (-2.0) mm long; lowest inflorescencebract short, delicate, the free portion 0.5-2 cm long.
12Perigynia 3.0-3.5 mm long, nerveless on the upper (ventral) face
1Basalsheaths brownish, lacking any purple coloration.
4 Widest leaf blade 11-25 mm wide; leaf blades of vegetative shoots 3.8-9.0 × as wide as bract leaves; bractblades from middle and basal portions of the culms 2.0-6.2 cm long; foliage glaucous
4 Widest leaf blade 2-14 mm wide; leaf blades of vegetative shoots 1.0-3.5 × as wide as bract leaves; bractblades from middle and basal portions of the culms 4.5-24 cm long; foliage green or glaucous.
7 Terminal spikes (1.0-) 1.2-2.7 mm wide; staminatescalesacute, those from the middle region of the staminatespike 3.6-5.5 mm long; vegetative shoots shorter than or slightly taller than the culms, the tallest vegetative shoot 0.5-1.3 (-1.8)× as tall as the tallest culm.
8 Terminal spike usually surpassing the bractblade of the distalmost lateralspike; longest (per plant) peduncle of terminal spike (6.3-) 8.1-15.9 cm long; widest leaf blade 2.0-2.9 (-3.5) mm wide; each perigynium face 7-10-nerved
8 Terminal spike usually surpassed by the bractblade of the distalmost lateralspike; longest (per plant) peduncle of terminal spike 0.9-7.2 (-11.4) cm long; widest leaf blade 2.7-4.5 (-5.3) mm wide; each perigynium face (8-) 11-15-nerved.
7 Terminal spikes 0.6-1.4 (-1.6) mm wide; staminatescalesobtuse, those from the middle region of the staminatespike 2.6-3.6 (-3.8) mm long; vegetative shoots much taller than the culms, the tallest vegetative shoot (1.4-) 1.7-3.7 (-4.9)× as tall as the tallest culm.
1 Plants monoecious, with 3-8 spikes per stem; leaf blades 4-8 mm wide, glaucous on the upper surface; [of the East Gulf Coastal Plain, east to sw. GA and Panhandle FL]
1 Plants dioecious, with a single unisexualspike per stem; leaf blades 2-4.5 mm wide, green on the upper surface; [of areas west of area, east to c. TN and nc. GA]
3 Leaf blades green, glabrous abaxially or sparsely hispidulous; perigynia (4.5-) 4.6- 5.6 (-6.2) × 1.9-2.2 (-2.3) mm; longest terminal spikes 14-34 (-42) mm long; [of ne. United States, south in our area to w. NC and w. VA]
6Perigynia 3.2-4.0 (-4.1) mm long, (1.5-) 1.8-2.3 (-2.5)× as long as wide; longest pistillatespike with (14-) 19-45 (-65) flowers, densely flowered, with the ratio [mm of spike length/number of flowers] = (0.56-) 0.67-1.1 (1.3); longest peduncle of staminatespike 0.5-15 (-31) mm long
6Perigynia (3.7-) 3.9-4.5 (-4.7) mm long, (1.9-) 2.1-2.6 (-2.8)× as long as wide; longest pistillatespike with 11-25 (-28) flowers, rather loosely flowered, with the ratio [mm of spike length/number of flowers] = (0.97-) 1.0-1.3 (1.6); longest peduncle of staminatespike (1.5-) 7.5-37 (-62) mm long
9Perigynia obtusely triangular in cross section, (2.2-) 2.5-3.1 × as long as wide, 1.5-1.9 (-2.2) mm wide; achenes (1.3-) 1.5-1.7 (-1.8) mm wide; achenestipes (0.3-) 0.4-0.6 mm long
9Perigyniaorbicular to suborbicular in cross section, 1.8-2.3 (-2.6)× as long as wide, (1.8-) 2-2.6 mm wide; achenes 1.7-2.1 (-2.2) mm wide; achenestipes (0.2-) 0.3-0.4 (-0.5) mm long
12Culmbases with purple-red to 0.3-2.4 (-7.3) cm high; widest leaf blades 3.3-8.0 (-9.1) mm wide; achenestipes (0.2-) 0.3-0.6 mm long.
13Perigynia (1.8-) 2.0-2.6 mm wide, orbicular to suborbicular in cross section; achene bodies (2.6-) 3.1-3.5 (-3.7) mm long; achenestipes (0.2-) 0.3-0.4 (-0.5) mm; achene bodies 4.8-9.7 (-12)× as long as the stipes
13Perigynia 1.5-2.3 (-2.4) mm wide, obtusely triangular in cross section; achene bodies 1.8-2.3 (-2.4) mm long; achenestipes (0.3-) 0.4-0.6 mm; achene bodies 3.2-5.8 (-7.3)× as long as the stipes.
14Perigynia 4.2-5.0 (-5.2) × 1.5-1.9 (-2.2) mm, (2.2-) 2.5-3.1× as long as wide; achene bodies broadly obovoid to oblong-obovoid, widest at a point 0.55-0.67 (-0.70) from base to tip of body
14Perigynia (3.6-) 3.9-4.5 (-4.7) × (1.7-) 1.8-2.3 (-2.4) mm, 1.8-2.3 (-2.5)× as long as wide; achene bodies broadly obdeltoid-obovoid, widest at a point (0.6-) 0.65-0.80 from base to tip of body
15Perigynia tightly enveloping achene or slightly inflated, obtusely triangular in cross section, 1.4-2.1 (-2.3) mm wide, (1.7-) 2.1-3.3× as long as wide.
18Perigynia (1.7-) 2.1-2.6× as long as wide, apex usually abruptly contracted; beak (0.3-) 0.5-1.2 mm long; longest lateralspike with 2-8 (-10) perigynia (including undeveloped or aborted ones)
19 Proximalmost spike usually considerably beyond base of culm; longest vegetative shoot 0.88-1.4× as long as the longest culm; proximalbracts with sheath front convex and elongated (0.8-) 1.1-4.0 mm beyond apex
18Perigynia (2.4-) 2.5-3.3× as long as wide, apex gradually tapering; beakless or the beak 0.1-0.4 mm; longest lateralspike with (5-) 7-14 perigynia (including undeveloped or aborted ones)
22 Longest (per plant) peduncle of terminal spike 0.9-3.2 (-6.8) cm long; two distalmost lateralspikes usually overlapping; longest vegetative shoot 1.4-2.2× as tall as the longest culm
22 Longest (per plant) peduncle of terminal spike (2.2-) 5.1-8.9 (-10.4) cm long; two distalmost lateralspikes usually widely separate or occasionally overlapping; longest vegetative shoot 0.5-1.3× as tall as the longest culm
1Achene on a stipe 0.5-1.5 mm long; perigynia (4.5-) 5.6-8.0 (-10) mm long; sterile shoots with leaves 2-8 mm wide; [native, collectively common and widespread in our area].
6Perigynia (6-) avg. 7.0 (-10) mm long, broadest below the middle, tapering with straight or slightly convex sides to a conspicuous beak with a hyaline tip; pistillatescalesobtuse; [of swamps, bogs, and other moist to wet habitats, nearly throughout our area]
6Perigynia (4.5-) avg. 5.6 (-7) mm long, broadest near the middle, tapering with concave sides to a short beak lacking a hyaline tip; pistillatescalesacute to acuminate (the lowest sometimes aristate); [of dry to moist upland forests and openings in the Mountains]
1Culm angles smooth below the inflorescence; rhizomes slender, 0.6-1.8 mm thick, shoots often arising 2-several in a cluster and many nodes without shoots
1Culm angles at least slightly scabrous below inflorescence; rhizomes coarse, 1.8-3 mm thick, typically with long unbranched segments from which shoots arise singly every few nodes.
2Beak of the perigynium 1/5 to 1/3 as long as the body; spikes 2-7 (-10); [exotic, naturalized primarily in brackish to salty coastal habitats]
5 Longest (per plant) staminate portion of terminal spike (4.9-) 5.8-13.5 mm long; proximalmost staminatescale in terminal spike 1.1-1.8 (-2.1) mm long, 13-26 (-35)% of length of staminate portion of terminal spike; perigyniumbeaks (1.9-) 2.3-3.9 mm long, 39-53% of perigynium length; shoot bases lacking red-purple; [of rich mesic forests widespread in our area, especially VA]
5 Longest (per plant) staminate portion of terminal spike 3.4-5.6 (-6.2) mm long; proximalmost staminatescale in terminal spike (1.9-) 2.1-3.3 mm long, (35-) 44-77% of length of staminate portion of terminal spike; perigyniumbeaks 1.4-2.3 (-2.5) mm long, 34-44% of perigynium length; shoot bases tinged with reddish-purple; [of c. TN and c. KY and westward]
6 Tallest culm 0.18-0.38× as tall as plant; perigynia (7.0-) 7.5-10.8 mm long; perigyniumbeaks (3.6-) 4.1-6.4 mm long; culms erect; peduncles usually erect to spreading
1Perigynia 2.3-3.9 (-4.2)× as long as wide, 0-5 (7)-veined abaxially (the veins extending unbroken from the perigyniumbase to the base of the perigyniumbeak); achenes 1.2-1.8× as long as wide; widest leaf blade (2.2-) 2.4-5.9 mm wide; [of uplands, south to n. NJ, n. PA, n. OH, n. IL]
1Perigynia (3.3-) 4.1-6.7× as long as wide, (3-) 4-8-veined abaxially (the veins extending unbroken from the perigyniumbase to the base of the perigyniumbeak); achenes 1.9-2.9 × as long as wide; widest leaf blade 1.3-4.4 mm wide; [of wetlands, collectively widespread].
2 Widest leaf (1.3-) 1.5-2.9 (-3.1) mm wide; culms (0.5-) 0.6-1.0 (-1.1) mm thick at mid-height; plant densely to loosely cespitose, the rhizomeinternodes 0.2-20 mm long; [of swamp forests and other wetlands, widespread in our area]
2 Widest leaf 2.8-4.4 mm wide; culms 1.0-1.6 mm thick at mid-height; plants densely cespitose, the rhizomeinternodes 0.2-1.0 (-8.5) mm long; [of seeps and bogs in the Blue Ridge and Blue Ridge Escarpment region of sw. VA, w. NC, e. TN, and nw. SC]
9 Lower perigynia mostly 2.8-4.8 mm long; lower perigynia (1.7-) 1.8-3.6× as long as wide; perigyniabeaks 0.95-2.0 mm long, mostly 0.45-0.85× as long as the perigynium body
9 Lower perigynia mostly 1.9-3.0 mm long; lower perigynia 1.0-2.0 (-2.2)× as long as wide; perigyniabeaks 0.4-0.95 mm long, mostly 0.2-0.5× as long as the perigynium body.
10Perigynia mostly 1-10-nerved over the achene on the adaxial surface; beak of perigynia more sparsely serrulate, with definite spaces between the often single teeth; perigynia more-or-less cuneate or concavely tapered from widest point to the beak, not forming a shoulder; [of a variety of situations, not generally calcareous].
11 Widest leaves 1.6-2.7 mm wide; infructescence mostly 18-45 mm long; [widespread in our area]
2Culms central, with the withered remains of the previous year’s leaves at the base; basalsheaths of fertile culms not at all or only slightly reddened; [of the Coastal Plain]
8 Longest ligules 2-10 (-12) mm long, < 2 × as long as wide; culms central, with the withered remains of the previous year’s leaves at the base; perigynia obscurely 10-15-veined; [of the Coastal Plain]
8 Longest ligules 13-40 (-56) mm long, much longer than wide; culmslateral, with bladeless sheaths at the base; perigynia usually strongly 14-28-veined; [of the Mountains in our area]
3 Principal leaves pliable, green, almost always without auricles, the summit of the sheaths U-shaped, only slightly prolonged beyond the collar; flat margins of perigynia 0.2-0.6 mm wide; achenes 1.0-1.7 mm wide; [of inland, non-maritime habitats].
4Perigynia erect-ascending, often veinless on the adaxial face or with a few veins of unequal strength, smooth; spikes 3-7 (-11), the uppermost often more-or-less separated
12Scales with white-hyaline or pale yellowish margins; perigynia greenish to straw-colored or pale brown, (2.3-) 2.5-4.0 (-4.2) mm long, often indistinctly 0-4 (-6) veined on the outer side
15Perigynia thin, often not winged to the base; leaf sheaths somewhat expanded toward the apex, bearing narrow wings continuous with the midvein and the edges of the leaf blade; leaves 3-7.5 mm wide; vegetative shoots tall, conspicuous, with numerous leaves spaced along the upper half of the culm.
17Inflorescences usually flexible, nodding at the tip, the lower spikes usually separated; perigynia usually 15-40, spreading at a 40-75 degree angle to the spikeaxis; leaf sheaths firm or friable at the summit
15Perigynia thick, winged to the base; leaf sheaths with more-or-less rounded edges, not distinctly expanded toward the apex; leaves 1-4.5 mm wide (except in C. normalis); vegetative shoots usually inconspicuous, with relatively few leaves clustered at the tip.
24Inflorescences on tallest culms elongate, more-or-less open toward the base, (2.5-) 3.0-5.1 × as long as wide, often arching or nodding at the tip; spikes more-or-less separate; lowermost internode (5-) 7-19 mm long, mostly 1/5-1/3 (-1/2) the length of the inflorescence.
34Sheaths smooth, summits concave, only reaching base of leaf blade; pistillatescales yellowish to reddish brown; [Interior Highlands and adjacent provinces, AR, LA, OK, and ne. TX]
38 Plants colonial, from creeping rhizomes; vegetative culms numerous, conspicuous, strongly 3-ranked, with 15-35 leaves when fully-developed; achenes 1.6-2 × as long as wide; larger spikes with 5-25 (-30) perigynia
38 Plants clumping; vegetative culms few, inconspicuous, usually with fewer than 15 leaves, not strikingly 3-ranked; achenes 1-1.6 (-1.7) × as long as wide; larger spikes with 15-80 perigynia.
40Perigynia 5.5-8.0 (-8.7) × (3.1-) 3.3-6.3 mm at largest (except sometimes in C. bicknellii and C. shinnersii), often prominently bulged on both faces; beak (1.4-) 1.6-2.5 (-3.4) mm long.
42 Leaf sheaths finely papillose, at least near apex; perigynia membranaceous, with brown achene clearly visible through hyalineadaxial face, usually with reddish brown tinged wings, strongly, evenly 4-8-veined adaxially over achene; pistillatescales usually reddish brown; anthers (2.4-)2.8-4.2 mm; plants in small clumps (usually fewer than 25 culms) in dry to mesic habitats
42 Leaf sheaths smooth; perigyniaherbaceous, opaque, with achene not clearly visible through adaxial face, with greenish or pale brown wings, finely and irregularly (0-)1-7-veined over achene adaxially; pistillatescales pale yellowish brown to brown; anthers (1.8-)2.2-3.6 mm; plants often in dense, large clumps (to 200 culms) in wet habitats.
40Perigynia 2.5-5.5 × 2.0-3.6 mm at largest (to 6.1 × 4.4 mm in the Florida endemicC. vexans), prominently bulged by achene only on abaxial face or flat; beak usually 0.7-1.6 (-1.8) mm long.
44 Leaf sheaths green-veined adaxially nearly to the summit; inflorescences dense to somewhat open, erect, the lowermost internode usually < 8 (-12) mm long
45Perigynia with acutebases, 2.0-2.8 mm wide; beakappressed, > 2/5 × the length of the body; broadest leaves 1.5-2.5 mm wide; [of sw. VA northward]
47 Leaf sheaths finely papillose (at magnification of 30-40 ×), especially near the leaf base.
48Perigynia strongly and evenly 4-8-veined over the achene adaxially, (4.5-) 5.1-5.5 mm long; pistillatescales usually (1.0-) 1.4-2.3 mm shorter than the perigynia; anthers (2.4-) 2.8-4.2 mm long
49Perigynia 2.3-3.5 mm wide; distance from summit of achene to tip of beak 1.8-3.1 mm; achenes 1.1-1.5 mm wide; spikeapex rounded or nearly acute; [Long Island west to n. OH and s. WI, northward]
49Perigynia 1.5-2.3(-2.5) mm wide; distance from summit of achene to tip of beak 0.8-1.7(-2) mm; achenes 1-1.3 mm wide; spikeapex rounded; [widespread throughout eastern and midwestern US]
50Spikes on larger culms (3-) 5-7 (-11), tapered at the base, the terminal spike with a conspicuous staminatebase; inflorescences typically open, 2.5-4.5 (-6.5) cm long, the lowermost internode (3-) 4-13 (-23) mm long; perigynium body (0.7-) 0.9-1.3 × as long as wide.
51Achenes 1.2-1.8 mm long, 1.0-1.3 mm wide; perigynia 2.5-4.2 mm long, 1.5-2.3 (-2.5) mm wide, mostly 2-4 (-6)-veined adaxially
54Perigynia veinless or faintly and irregularly 1-5-veined over the achene adaxially, more-or-less orbicular, the bodies (2-) 2.3-3.2 mm long, (0.7-) 0.9-1.1 (-1.3) × as long as wide; pistillatescales mostly acute, about as long as to 0.7 (-0.9) mm shorter than the subtended perigynium (flattened and measured separately)
54Perigynia strongly 4-6-veined over the achene adaxially, broadly ovate to broadly elliptic, (or rarely nearly orbicular), the bodies (2.7-) 3-4 mm long, (0.9-) 1.0-1.6 × as long as wide; pistillatescales mostly obtuse, 0.7-1.7 mm shorter than the subtended perigynium (flattened and measured separately)
4Spikes 9-14 (-15) mm thick; widest leaves 2.4-4.0 (-5) mm wide; spikes usually 2.5-3.5× as long as wide; perigynia 4.8-6.6 (-7.6) mm long, the beaks usually 0.7-1.3× as long as the body
4Spikes (12-) 15-22 mm thick; widest leaves (4.0-) 4.5-13 mm wide; spikes usually < 2.5× as long as wide if < 15 mm thick; perigynia (6-) 6.5 (-10.8) mm long, the beaks 0.6-0.9× as long as the body
5Perigynia ± reflexed when mature, leathery, uninflated, compressed-triangular, strongly and closely veined with most veins separated by less than 2× their width; longest beak teeth 0.7-2.1 (-2.8) mm long.
6Spikes 12-18 mm thick; beak teeth strongly out-curved, longest 1.3-2.1 (-2.8) mm long
7 Leaves filiform-involute, wiry, (0.5-) 1-3 (-3.2) mm wide; stems smooth, round or obtusely trigonous in cross-section; [rare, in cool temperate peatlands northward and limited to high elevation mountain bogs southward]
7 Leaves flat, U-, V-, or W-shaped in cross-section, the widest 1.5-12 (-15) mm wide; stems often scabrous-angled, round to trigonous; [collectively widespread].
8Achenes asymmetrical, deeply indented or invaginated on one face; widest perigynia (4.0-) 4.5-7 mm wide; beaks 2.4-4.8 mm long, smooth
13 Plant colonial from long-creeping rhizomes; widest leaves (4.5-) 5-12 (-15) mm wide; ligules about as long as wide; basalsheaths usually spongy-thickened and only slightly or not red-tinged
8Achenes lacking a constriction or indentation, the persistentbeak usually erect, the body 1.7-1.9 × (1.2-) 1.3-1.6 mm; perigynia (2.4-) 2.8-3.4 × (1.8-) 1.9-2.5 (-2.6) mm, obovate to broad-obovate in outline, rounded at the apex, moderately inflated, with a beak 0.2-0.5 mm long; carpellatescales in the lower ¼ of the
spike with awns 2.3-4.2 (-5.1) mm long
(c) Hartley, Nate - CC-BY-NC, permission granted to NCBG
8Achenes with a constriction or indentation on one margin or rarely across one face and then the achene not plane, the persistentbeak often bent and projecting at an angle, the body 1.5-1.8 (-1.9) × 1.2-1.4 mm; perigynia 2.1-3 × 1.3-2 (-2.2) mm, broad-elliptic to obovate in outline, obtuse to rounded at apex, weakly to
moderately inflated, with a beak 0.1-0.3 (-0.4) mm long; carpellatescales in the lower ¼ of the spike with awns (3-) 3.9-9.5 mm long
3Perigynia 3-5 mm wide at the widest point; achenes broadest above the middle, with a pronounced shoulder rounding abruptly to the tip; style of mature achene with a half to full coil in its lower portion; [of high elevations in our area, generally in spruce-fir or northern hardwoods forests]
3Perigynia 5-8 mm wide at the widest point; achenes broadest at the middle, smoothly rounded to the tip; style of mature achene straight or arcuate; [widespread in our area]
1Sheath of uppermost leaf usually > 1.7 cm long; beaks of perigynia 4.5-10 mm long, generally > 1/2 the length of the entire perygynium; teeth at tip of perigyniumbeak with < 5 scabrules on inner side; achenes with rhombic or nearly triangular sides; achene surfaces smooth at 50× magnification; [subsection Lupulinae].
4Base of lowest staminatespike overtopping the tip of the pistillatespikes by 2.3-7.5 cm in the longest culms; mature achenes (1.5-) avg. 1.8 (-2.0) mm wide, mostly flat‐sided in cross‐section; leaves 3-5 mm wide; plants always long‐rhizomatous, forming extensive patches
4Base of the lowest staminatespike overlapping with the pistillatespikes or overtopping them by < 2.2 cm in the longest culms; mature fruits (1.9-) avg. 2.6 (-3.8 mm wide, concave in cross‐section (rarely flat‐sided in C. lupulina); leaves 3-12 mm wide; plants cespitose to long‐rhizomatous.
5Achene body (2.8-) avg. 3.3 (-3.7) mm long, (1.1-) avg. 1.4 (-1.7) × as long as wide; achene edges without distinct knobs or acute upturned angles, the outline smoothly curved without an inflexion point; achene length at 1/8th the width > 1.10 mm; perigynia densely arrayed in the spikes (except for depauperate individuals), (12-) avg. 17 (-24) perigynia per cm in the middle of the spike, these spreading at an angle of (40-) avg. 50 (-70) degrees from
the vertical
5Achene body (1.9-) avg. 2.6 (-–3.1) mm long, (0.7-) avg. 1.0 (-1.2) × as long as wide; achene edges with distinct knobs or acute upturned angles (often rounded in C. gigantea but then the achene bodies clearly wider than long); achene length at 1/8th the width < 1.10 mm, perigynia less densely arrayed in the spikes, (6.6- avg. 13 (-18) perigynia per cm, these spreading at an angle of (45-) avg. 60 (-90) degrees from the vertical.
6Perigynia green with a slight orange tinge when mature,
spreading at an angle of (45-) avg. 60 (-70) degrees from the vertical; perigynium body (excluding the border of the stigma aperture) with (2.9-) avg. 15 (-30) scabrules; distance between the apex of the achene body and the start of the style curve (0.2-) avg. 0.6 (-1.2) mm
6Perigynia green when mature, drying brown and without an orange tinge, these spreading at an angle of (60-) avg. 80 (-90) degrees from the vertical; perigynium body with (0-) avg. 0.2 (-3) scabrules; distance between the apex of the achene body and the start of the style curve (1.1-) avg. 1.6 (-2.3) mm (or the style rarely straight in C. gigantea).
7 Widest leaf (3-) avg. 5.5 (-7.5) mm wide; perigynium
gradually narrowed into a beak, (1.3-) 1.4–2.8 (-3.2) mm wide at half its length; achene body length at 1/8th of its width 25-37% of total length of achene body; longest pistillatespike with (11-) avg. 16 (-27) perigynia; plants strictly long‐rhizomatous
7 Widest leaf (5.5-) avg. 12 (-13) mm wide; perigynium abruptly
narrowed into the beak, (0.5–) 0.7-1.4 (-1.6) mm wide at half its length; achene body length at 1/8th of its width (32-) 35-50 (-52)% of the total length of the achene body; longest pistillatespike with (25-) avg. 38 (-65) perigynia; plants cespitose to long‐rhizomatous
3Pistillatescales usually awned (rarely merely cuspidate); pistillatescales (including the awn, if present) 0.5-1.2× as long as the perigynia; larger achenes 3.4-4.0 (-4.5) mm long (ca. (1.7-2.4x as long as wide); widest leaves of vegetative shoots 8-18 (-21) mm wide; pistillatespikes normally not staminate at apex (rarely with a few staminate flowers); [primarily of the Mountains and Piedmont]
4 Larger pistillatespikes 10.5-13.5 (14.0) mm wide (measured beak tip to beak tip); longer perigyniumbeaks 2.3-3.2 mm long; [MI south to extreme s. OH and c. IN]
5 Terminal (staminate) spike 12-21 mm long; pistillatespikes (1-) 2-5 per culm; tallest culms of a plant 2.5-5 dm tall; achenes 1.0-1.2 mm wide; [of acid situations in NJ, n. OH, n. IN, and northward]
26 Leaf blades, at least toward the tip, M-shaped in cross-section when young, the upper surface usually with 2 marginal veins more prominent than the midvein; staminatespikes 1-4