1 Pistillate spikes all from the
base of the plant
1 Pistillate spikes all or in part borne on the elongate, aboveground stem.
2 Bracts of the lowermost non-
basal spike with well-developed
sheath > 4 mm long.
3 Beak of
perigynium with distinct teeth > 0.6 mm long
3 Beak of
perigynium entire , notched, or with indistinct teeth < 0.6 mm long.
4 Bracts of the lowermost non-
basal spike bladeless, or with a
blade < 2 mm long.
5 Perigynia 2.0-2.9 mm long; leaf
blades 0.9-3.3 mm wide
5 Perigynia 4-5 mm long; leaf
blades 4-8 mm wide
4 Bracts of the lowermost non-
basal spike with
blade > 3 mm long (and often much longer).
6 Achene tip with at most a short
apiculus .
7 Leaves usually
glabrous , to
scabrous on the veins.
8 Bases of plants distinctly red or purple.
9 Lowermost
pistillate scales awned; leaves somewhat
septate -
nodulose ; plants usually long-
rhizomatous and forming large
clonal colonies
2 Bracts of the lowermost non-
basal spike sheathless or with
sheath < 4 mm long.
10 Perigynia > 10 mm long.
11 Pistillate spikes globose , about as long as wide;
staminate spikes usually 1
10 Perigynia < 10 mm long.
12 Perigynium beak with 2 teeth > 0.6 mm long
12 Perigynium beak entire or with teeth < 0.6 mm long.
13 Terminal
spike staminate (or rarely
androgynous ).
16 Leaf
sheaths (and usually the
blades as well)
pubescent .
18 Perigynia usually < 3.2 mm long, the
apex rounded and beakless, or abruptly beaked
18 Perigynia > 3.5 mm long, the tip tapering or abruptly beaked.
19 Longer
peduncles of
pistillate spikes > 1 cm long;
perigynia > 3× as long as wide, tapering gradually to the
base
19 Longer
peduncles of
pistillate spikes 0-1 cm long;
perigynia < 3× as long as wide, abruptly
contracted to a short
stipe at the
base .
20 Perigynia distinctly 20-30-veined;
beak < 0.5 mm long
20 Perigynia veinless except for 2
marginal veins;
beak > 0.7 mm long
21 Achene tip with at most a short
apiculus .
22 Leaf
blades scabrous on the upper surface;
beak of
perigynium recurved
22 Leaf
blades glabrous on the upper surface, often with rough
margins or tip;
beak of
perigynium straight.
23 Fronts of
sheaths of lower leaves ladder-
fibrillose ; leaves and
sheaths septate -
nodulose (sometimes obscurely so)
23 Fronts of leaf
sheaths not ladder-
fibrillose , sometimes breaking into
longitudinal fibers; leaves and
sheaths not
septate -
nodulose .
24 Perigynia strongly 12-30-veined.
25 Pistillate scales with 3-7 (-10) veins
25 Pistillate scales with 1-3 veins.
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 ;
staminate spikes 1-4
26 Leaf
blades V-shaped in cross-section when young, the upper surface lacking 2
marginal veins more prominent than the
midrib ;
staminate spike 1
24 Perigynia 0-12-veined.
28 Plants with at least some
pistillate spikes basal ;
culms much shorter than the leaves
28 Plants with most
pistillate spikes on obvious elongated stems;
culms shorter than or longer than the leaves.
29 Upper leaves with
blades > 2 cm long, longer than the
sheaths
29 Upper leaves bladeless or with
blades < 1 cm long and also shorter than the
sheaths
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
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.
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 1-6;
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 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.
22 Lower
pistillate scales with
awn 1.2-3.5 mm long;
staminate scales awned
18 Perigynia not
papillose , essentially smooth.
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
29 Perigynia ascending , spreading at about right angles, or
reflexed when mature
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
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