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Published In: Species Plantarum 2: 972. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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3. Carex L. (sedge)

(Mackenzie, 1931–1935)

Plants perennial, monoecious or rarely dioecious, usually with short- or long-creeping rhizomes. Aerial stems 1 to many per plant, erect to arched or spreading, usually solid, unbranched, bluntly to sharply triangular in cross-section, glabrous or roughened, the plants sometimes producing separate fertile and vegetative stems. Leaves few to many, basal and often also alternate (3-ranked), with well-developed leaf blades or the lowermost leaves sometimes reduced to bladeless sheaths, the sheath with a scaly to papery ligule, the leaf blade spreading to ascending, flat or somewhat folded lengthwise, the margins sometimes inrolled. Inflorescences terminal and sometimes also in the upper leaf axils, composed of spikes, these 1 to many per stem, sessile or stalked, in spikes, racemes, or panicles, rarely in loose clusters or single. Spikes containing all staminate or all pistillate flowers or a mixture of both flower types; if a mixture then the staminate flowers either at the base of the spike or at the tip, often subtended by a sometimes reduced, leaflike bract, the flowers spirally alternate, usually dense, each subtended by a scale. Perianth (bristles or scales) absent. Staminate flowers with 3 stamens. Pistillate flowers with a single ovary, this loosely or tightly enclosed in (but not fused to) a perigynium (saclike structure ), this sometimes beaked or winged, and usually with 2 or more nerves. Styles not expanded at the base, not persisting on the fruit as a tubercle. Stigmas 2 or 3, protruding from a small opening at the tip of the perigynium. Fruits biconvex or 3-angled, sometimes somewhat flattened, enclosed in and shed with the perigynium. 1,500–2,000(–2,500) species, worldwide, most diverse in temperate to arctic regions.

Carex is the largest and arguably the most difficult genus in the Missouri flora. Species are sometimes separable consistently only by using technical characters of the spikes, scales, perigynia, and fruits. Flowering specimens may be impossible to determine with confidence. Characters of the rhizomes and vegetative stems may be important in species identification. For purposes of this treatment, perigynium length measurements include any beak present. The leaf sheath is often discussed as having two sides, the “dorsal” side, where the leaf blade is attached to the sheath, and the “ventral” side, opposite the leaf blade. Similarly, the perigynia, if flattened or otherwise differentiated into two sides, have the ‘dorsal’ (outer) side facing away from the axis of the spike and the ‘ventral’ (inner) side facing toward the center of the spike.

The basic unit of the Carex inflorescence is referred to as a spike or spikelet in the botanical literature. It is structurally different from the spike type of inflorescence found in various angiosperm families, as well as from the spikelets of the Poaceae or even other genera of Cyperaceae. In some species of Carex, the perigynium contains a reduced rachilla (axis) along the ovary. The perigynium thus can be interpreted as a bract that has become fused around a short inflorescence branch, which has been reduced to a single functional flower (Reznicek, 1990; Gleason and Cronquist, 1991). The term spike is used here for the sake of convenience and consistency with the majority of literature on the genus. The structures referred to as flowers (to avoid introducing more specialized terminology) in the genus also are unlike other flowers, in that they represent reduced inflorescence branches.

The genus usually is classified into four subgenera, Carex, Indocarex Baillon, Primocarex Kük., and Vignea (P. Beauv. ex T. Lestib.) Kük. The mainly Old World Indocarex grows only in the tropics, but the other three occur in Missouri. Some botanists do not distinguish subgenus Primocarex (in Missouri, only C. leptalea), which consists of various species groups in which the inflorescence contains only a single spike. Distinctions between these groups are complicated and rely upon combinations of inflorescence and flower characters. For our purposes, subgenus Vignea includes species with two stigmas and relatively short, sessile, lateral spikes usually containing both pistillate and staminate flowers. Subgenus Carex (subgenus Eucarex Coss. & Germ.) contains all of the species with three stigmas, as well as the C. aquatilis complex (section Phacocystis), which includes species with two stigmas in which most of the lateral spikes are elongate and contain only pistillate flowers.

Each of the subgenera of Carex has been further subdivided into a number of sections, which provide a more pragmatic level of classification at which to approach the study of the state’s sedges. Learning to recognize the common sections of Missouri sedges in the field can greatly simplify the process of determining species. The present treatment of Carex differs most markedly from that of Steyermark (1963) in the elimination of the single key to all sedge species, which proved difficult for many users to follow. Instead, the key to sections has been expanded, with separate keys to species at the beginning of each sectional treatment. The delimitations of sections and species are in general agreement with those in a forthcoming volume of the Flora of North America series, and were completed in consultation with A. A. Reznicek of the University of Michigan, who is helping to coordinate the production of Carex treatments for that work. The sectional classification differs somewhat from that of Steyermark (1963), but no attempt has been made in the present treatment to provide synonymy for sectional names.

The following key to the sections of Carex incorporates characters of leaves, stems, and pubescence where possible; thus several sections appear in more than one place in the key.

 

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1 Aerial stems with only 1 spike (do not confuse densely spaced, multiple spikes for single spikes) (2)
+ Aerial stems with 2 or more spikes (5)
2 (1) Spike with all staminate or all pistillate flowers 1 Carex sect. Acrocystis
+ Spike with both staminate and pistillate flowers (3)
3 (2) Spike with the staminate flowers toward the base 28 Carex sect. Squarrosae
+ Spike with the staminate flowers toward the tip (4)
4 (3) Lowermost pistillate scale 15–50 mm long, leaflike 24 Carex sect. Phyllostachyae
+ Pistillate scales 2.5–5.0 mm long, not leaflike 25 Carex sect. Polytrichoideae
5 (1) Stigmas 2; fruits biconvex, sometimes unevenly so (1 side flat, the other rounded) (6)
+ Stigmas 3; fruits slightly to strongly trigonous, sometimes circular in cross-section or nearly so (23)
6 (5) Some or all of the spikes completely staminate or completely pistillate, distinctly different in size and appearance, or the plants dioecious (7)
+ All spikes more or less similar in size and appearance, usually containing both staminate and pistillate flowers (except in section Stellulatae) (10)
7 (6) Inflorescences open to somewhat dense, the spikes all distinctly separated, mostly 3–20 times as long as wide (8)
+ Inflorescences very dense, composed of a more or less continuous cluster of short spikes that are 1–2 times as long as wide, the individual spikes sometimes difficult to differentiate (9)
8 (7) Pistillate spikes 30–110 mm long, with numerous perigynia 22 Carex sect. Phacocystis
+ Pistillate spikes 3–13 mm long, with 5–25 perigynia 29 Carex sect. Stellulatae
9 (7) Leaves all clustered near the base of the plant, 1–3 mm wide, the sheaths white to light brown on the ventral side, unlined 9 Carex sect. Divisae
+ Leaves basal and noticeably alternate along the lower half of the aerial stems, 2–5 mm wide, the sheaths mostly green and with a fine pattern of vertical, green lines along the ventral side 14 Carex sect. Intermediae
10 (6) Plants with the rhizomes well developed and long-creeping, forming loose colonies of tufts, or the aerial stems well spaced and not tufted (11)
+ Plants with the rhizomes short-creeping or poorly developed, forming dense tufts or clumps (13)
11 (10) Inflorescences open, the spikes all or mostly distinctly separated 23 Carex sect. Phaestoglochin
+ Inflorescences very dense, the individual spikes sometimes difficult to differentiate (12)
12 (11) Leaves all clustered near the base of the plant, 1–3 mm wide, the sheaths white to light brown on the ventral side, unlined 9 Carex sect. Divisae
+ Leaves basal and noticeably alternate along the lower half of the aerial stems, 2–5 mm wide, the sheaths mostly green and with a fine pattern of vertical, green lines along the ventral side 14 Carex sect. Intermediae
13 (10) Staminate flowers at the bases of some or all of the spikes (if stamens have fallen from older spikes, locate the position of the densely overlapping or empty scales of the staminate portions), the spikes often appearing tapered at the base (14)
+ Staminate flowers at the tips of some or all of the spikelets (if stamens have fallen from older spikes, locate the position of the densely overlapping or empty scales of the staminate portions), the spikes usually appearing abruptly rounded or truncate at the base (17)
14 (13) Perigynia flattened, the margins with prominent, thin wings, at least on the beak and apical portion of the body (15)
+ Perigynia plump, or if somewhat flattened then the margins rounded to angled or narrowly ridged, but not winged (16)
15 (14) Bracts leaflike, much longer than the inflorescence (to 20 cm long) 7 Carex sect. Cyperoideae
+ Bracts reduced, shorter and narrower than the leaves, shorter than the inflorescence or nearly so 18 Carex sect. Ovales
16 (14) Perigynia all ascending to nearly erect 8 Carex sect. Deweyanae
+ Perigynia mostly spreading or reflexed, occasionally ascending 29 Carex sect. Stellulatae
17 (13) Perigynia thin-walled, with the base noticeably corky- or spongy-thickened at maturity (test base with a needle or forceps to see mass of soft tissue around the base of the fruit) (18)
+ Perigynia thick- or thin-walled, but not noticeably corky- or spongy-thickened at the base (sometimes slightly and inconspicuously spongy-based in section Phaestoglochin) (20)
18 (17) Spikes more than 10 per inflorescence, usually numerous, at least the lowermost nodes usually with more than 1 spike (inflorescence compound) 32 Carex sect. Vulpinae
+ Spikes mostly less than 10 per inflorescence, 1 per node (inflorescence unbranched) (19)
19 (18) Lateral spikes with both pistillate and staminate flowers, the staminate flowers relatively few and inconspicuous; perigynia green, straw-colored, or less commonly tan at maturity 23 Carex sect. Phaestoglochin
+ Lateral spikes mostly all staminate or all pistillate, less commonly with a few pistillate flowers scattered in an otherwise staminate spike; perigynia turning brown at maturity 29 Carex sect. Stellulatae
20 (17) Inflorescence compound, with lower branches conspicuous, to 4 cm long; perigynia dark brown to olive green or nearly black at maturity 12 Carex sect. Heleoglochin
+ Inflorescence unbranched, or if compound then the lower nodes with the clusters of spikes sessile or on short branches; perigynia green, straw-colored, yellow, tan, or brown at maturity (21)
21 (20) Inflorescences compound, the lowermost nodes with 2 or more spikes; spikes numerous; stems bluntly to sharply trigonous, but firm and not winged 17 Carex sect. Multiflorae
+ Inflorescences with the spikes 1 per node, or if compound then the stems sharply trigonous, narrowly winged, and easily crushed; if the inflorescence is too dense to distinguish the number of spikes per node, then the spikes 10 or fewer (22)
22 (21) Lateral spikes with both pistillate and staminate flowers, the staminate flowers relatively few and inconspicuous; perigynia green, straw-colored, or less commonly tan at maturity 23 Carex sect. Phaestoglochin
+ Lateral spikes mostly all staminate or all pistillate, less commonly with a few pistillate flowers scattered in an otherwise staminate spike; perigynia turning brown at maturity 29 Carex sect. Stellulatae
23 (5) All or part of the leaf sheaths, leaf blades, bracts, and/or aerial stems hairy (plants that are otherwise glabrous, with leaves or stems minutely roughened or finely toothed along the margins, should be keyed as being glabrous) (24)
+ Leaf sheaths, leaf blades, bracts, and aerial stems glabrous (leaves or stems sometimes minutely roughened or finely toothed along the margins) (30)
24 (23) Perigynia with the body hairy (25)
+ Perigynia with the body glabrous (beaks sometimes minutely roughened or toothed) (26)
25 (24) Terminal spike entirely staminate 30 Carex sect. Triquetrae
+ Terminal spike mostly pistillate, with staminate flowers at the base 26 Carex sect. Porocystis
26 (24) Terminal spike entirely staminate (rarely a few pistillate flowers present at tip or base) (27)
+ Terminal spike with pistillate flowers toward the tip and staminate flowers toward the base (29)
27 (26) Plants with the rhizomes well developed and long-creeping, forming loose colonies, the aerial stems well spaced; perigynia 7–12 mm long 5 Carex sect. Carex
+ Plants with the rhizomes short-creeping or poorly developed, forming dense tufts or clumps; perigynia 4.5–7.0 mm long (28)
28 (27) Pistillate spikes with 2–8 perigynia; basal leaf sheaths brown, lacking reddish purple or purple coloration 11 Carex sect. Griseae
+ Pistillate spikes with 9–25 perigynia; basal leaf sheaths tinged with reddish purple or purple 13 Carex sect. Hymenochlaenae
29 (26) Lateral spikes 18–45 mm long, 6–8 times as long as broad, linear to narrowly oblong in outline 13 Carex sect. Hymenochlaenae
+ Lateral spikes 5–20 mm long, 1–4 times as long as broad, narrowly ovate to narrowly oblong in outline 26 Carex sect. Porocystis
30 (23) Perigynia with the body hairy or roughened with minute, stiff hairs (perigynia with bodies minutely pebbled, papillose, or resin-dotted should be keyed as being glabrous) (31)
+ Perigynia with the body glabrous (beaks sometimes minutely roughened or toothed, or bodies occasionally minutely pebbled or papillose) (37)
31 (30) Perigynia 12–20 mm long; pistillate spikes 20–40 mm wide 16 Carex sect. Lupulinae
+ Perigynia less than 10 mm long; pistillate spikes less than 15 mm wide (32)
32 (31) Flowering stems 1–20 cm long, most or all of them shorter than and/or hidden by the leaf blades 1 Carex sect. Acrocystis
+ Flowering stems 20–120 cm long, or if shorter than 20 cm then longer than and not hidden by the leaf blades (33)
33 (32) Terminal spike with pistillate flowers toward the tip and staminate flowers toward the base 26 Carex sect. Porocystis
+ Terminal spike entirely staminate (34)
34 (33) Pistillate spikes 3–9 mm long, 1–2 times as long as wide; aerial stems 5–50 cm long 1 Carex sect. Acrocystis
+ Pistillate spikes 10–90 mm long, 3–6 times as long as wide; aerial stems 40–90 cm long (35)
35 (34) Perigynia roughened with minute, stiff hairs, the beak somewhat curved; basal leaf sheaths lacking reddish purple to purple coloration 3 Carex sect. Anomalae
+ Perigynia not roughened, lacking a beak or the beak straight; basal leaf sheaths tinged with reddish purple or purple (36)
36 (35) Perigynia 5–10 mm long, tapering to a prominent beak ending in 2 teeth 0.9–3.0 mm long 5 Carex sect. Carex
+ Perigynia 3.0–4.5 mm long, narrowed abruptly to a short beak ending in 2 teeth 0.3–0.9 mm long 19 Carex sect. Paludosae
37 (30) Terminal spike with pistillate flowers toward the tip and staminate flowers toward the base (38)
+ Terminal spike entirely staminate or with a few perigynia at the base (note that the terminal spike may sometimes be overtopped by longer or stalked, lateral, pistillate spikes) (42)
38 (37) Spikes 10–22 mm wide at maturity; perigynia 3.5–8.5 mm long 28 Carex sect. Squarrosae
+ Spikes 2–8 mm wide at maturity; perigynia 2–4 mm long (39)
39 (38) Perigynia with distinct, well-developed beaks; at least some of the lowermost spikes spreading to drooping and long-stalked 13 Carex sect. Hymenochlaenae
+ Perigynia lacking beaks or with short, poorly developed beaks; spikes all erect or ascending (40)
40 (39) Perigynia grayish white, the surface minutely pebbled or papillose; plants with well-developed, long-creeping rhizomes, not forming dense tufts or clumps 4 Carex sect. Atratae
+ Perigynia olive green to dark brown, the surface not pebbled or papillose; plants with short-creeping or poorly developed rhizomes, forming dense tufts or clumps (41)
41 (40) Perigynia distinctly longer than wide, with 1 or more nerves, ascending on the spike 26 Carex sect. Porocystis
+ Perigynia about as long as wide, nerveless, spreading at a right angle to the axis of the spike 27 Carex sect. Shortianae
42 (37) Perigynia 10–20 mm long at maturity 16 Carex sect. Lupulinae
+ Perigynia 2–9(–10) mm long at maturity (43)
43 (42) Lowermost (or only) pistillate spike with the bract absent or reduced to a tubular sheath, the blade absent or short-triangular (do not confuse the bract of the spike with the lowermost pistillate scale, which subtends a perigynium and may be leaflike in section Phyllostachyae) (44)
+ Lowermost pistillate spike with the bract having a well-developed, leaflike blade (the sheath may be absent or present) (46)
44 (43) Spikes all staminate toward the tip and with 2–4 perigynia toward the base, the lowermost (or only) spike without a bract; however, the lowermost pistillate scale 15–50 mm long, leaflike 24 Carex sect. Phyllostachyae
+ Terminal spike entirely staminate or rarely with a few perigynia at the base, the other spike(s) all pistillate; lowermost (or only) pistillate spike with the bract reduced to a tubular sheath, the blade absent or short-triangular; pistillate scales 1.2–4.0 mm long, not leaflike (45)
45 (44) Pistillate spikes mostly basal and long-stalked, often hidden among the leaf bases, but when associated with a staminate spike, then 1–2, sessile, and not overtopping the terminal, staminate spike; perigynia 2.5–4.0 mm long 1 Carex sect. Acrocystis
+ Pistillate spikes 2–4, lateral, on long stalks and overtopping the staminate spike; perigynia 1.5–2.0 mm long 2 Carex sect. Albae
46 (43) Pistillate spikes with 1–9 perigynia (47)
+ Pistillate spikes with 10 to numerous perigynia (50)
47 (46) Perigynia pale green, usually glaucous; plants with the rhizomes well developed and long-creeping, the aerial stems mostly arising singly 20 Carex sect. Paniceae
+ Perigynia olive green to dark green or brown, not glaucous; plants with the rhizomes short-creeping or poorly developed (except in C. abscondita of the Careyanae), the aerial stems arising from tufts or clumps (48)
48 (47) Perigynia with the numerous nerves impressed (most easily seen in dried specimens); pistillate scales with rough-margined awns 11 Carex sect. Griseae
+ Perigynia with the usually numerous nerves raised; pistillate scales lacking awns or with the awns smooth-margined (49)
49 (48) Perigynia sharply trigonous with the sides flat or nearly so and with more than 40 nerves 6 Carex sect. Careyanae
+ Perigynia bluntly trigonous with the sides convex, at least in the lower half and with 25 or fewer nerves 15 Carex sect. Laxiflorae
50 (46) Styles persistent, not jointed to and forming a hard, bony beak similar in texture to the main body of the fruit; perigynia usually prominently beaked, the beak ending in 2 stiff, short to long teeth (51)
+ Styles withering during fruit development, jointed to the main body of the fruit, which is beakless or short-beaked at maturity; perigynia lacking a beak or with the beak lacking well-developed teeth at the tip, appearing cut-off or with short, soft, inconspicuous teeth (55)
51 (50) Staminate spike 1 per inflorescence (52)
+ Staminate spikes 2–6 per inflorescence (53)
52 (51) Perigynia with the main body obovate to obtriangular in outline, widest above the middle, truncate or abruptly narrowed to the beak 28 Carex sect. Squarrosae
+ Perigynia narrowly to broadly ovate in outline, widest at or below the middle, tapered more or less gradually to the beak 31 Carex sect. Vesicariae
53 (51) Plants with the rhizomes short-creeping or poorly developed, forming dense tufts or clumps; perigynia thin-walled, papery 31 Carex sect. Vesicariae
+ Plants with the rhizomes well developed and long-creeping, forming large colonies; perigynia thick-walled, firm or leathery (54)
54 (53) Perigynia with teeth 1.0–2.2 mm long; fruits with the stylar beak straight at maturity 5 Carex sect. Carex
+ Perigynia with the teeth 0.3–1.0 mm long; fruits with the stylar beak bent or curved abruptly near the base 19 Carex sect. Paludosae
55 (50) Bract of the lowest pistillate spike lacking a sheath or nearly so 21 Carex sect. Pendulinae
+ Bract of the lowest pistillate spike (not to be confused with the scales of the lowermost perigynia) with a well-developed, tubular sheath (56)
56 (55) At least the lowermost pistillate spike with long, thin stalks, spreading, nodding, or drooping at maturity (57)
+ Spikes variously sessile or stalked, but all erect or ascending (58)
57 (56) Pistillate spikes mostly spreading, nodding, or drooping, 20–60 mm long, or if less than 20 mm long then the perigynia abruptly narrowed to a slender beak about as long as the main body 13 Carex sect. Hymenochlaenae
+ Pistillate spikes mostly erect to ascending, only the lowermost spreading, 6–20 mm long; perigynia without beaks or with tapered beaks much shorter than the main body 15 Carex sect. Laxiflorae
58 (56) Plants with the rhizomes well developed and long-creeping, the aerial stems mostly arising singly (59)
+ Plants with the rhizomes short-creeping or poorly developed, forming tufts or clumps (60)
59 (58) Perigynia green to brown, not pale or glaucous, broadest at or below the middle, rounded at the base, loosely enveloping the fruit; leaf blades smooth on the undersurface 10 Carex sect. Granulares
+ Perigynia pale green to pale brown or nearly white, often somewhat glaucous, broadest above the middle, tapered at the base, tightly enveloping the fruit; leaf blades with minute papillae on the undersurface 20 Carex sect. Paniceae
60 (58) Perigynia with the nerves impressed (more easily seen in dried specimens) 11 Carex sect. Griseae
+ Perigynia with the nerves raised (61)
61 (60) Perigynia rounded at the base, obscurely trigonous to nearly circular in cross-section; stems bluntly trigonous, firm and not easily compressed 10 Carex sect. Granulares
+ Perigynia tapered at the base, strongly trigonous in cross-section, but with convex sides, at least below the middle; stems strongly trigonous, soft and easily compressed 15 Carex sect. Laxiflorae
 

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