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FOC | Family List | FOC Vol. 23 | Cyperaceae

15. Cyperus Linnaeus, Sp. Pl. 1: 44. 1753.

莎草属 suo cao shu

Authors: Lun-Kai Dai, Gordon C. Tucker & David A. Simpson

Cyperus sect. Juncellus Grisebach; Juncellus (Grisebach) C. B. Clarke; Mariscus Vahl; Torulinium Desvaux ex Hamilton.

Herbs, annual or perennial, with rhizomes or stolons. Culms caespitose or solitary, erect, usually 3-angled or acutely triquetrous, sometimes compressed triquetrous, stout or slender, leafy at basal part or at base. Leaves basal, 3-ranked, rarely without a blade; ligule absent. Involucral bracts leaflike, usually 2-10(-20 or more), at base of inflorescence. Inflorescences terminal, a simple or compound anthela, with several to many rays and usually with raylets (secondary rays); rays and raylets unequal or rarely equal in length or inflorescence capitate. Spikelets few to many in spikes, digitate clusters, or a capitulum at apex of rays, rarely single; rachilla not articulate at base, persistent, usually with narrow wings. Glumes distichous, rarely spirally imbricate; basal 1 or 2 glumes without a flower; remaining glumes each with a bisexual flower. Perianth bristles or scales absent. Stamens (1-)3. Style base not swollen; stigmas (2 or)3, deciduous at maturity. Nutlet 3-sided, smooth, puncticulate, tuberculate, or rarely reticulately striate.

About 600 species: temperate, subtropical, and tropical regions worldwide; 62 species (eight endemic, four introduced) in China.

1 Spikelets digitate or fasciculate on a very short rachis, or inflorescences capitate or globose   (2)
+ Spikelets in spikes terminating rays (rachis (0.5-)1-6 cm, usually visible, sometimes covered by bases of spikelets in pressed specimens)   (31)
2 (1) Inflorescences capitate or anthelate, with very short rays (rarely with 1 or 2 elongated rays)   (3)
+ Inflorescences anthelate, with elongate rays, sometimes with secondary (compound) and tertiary (decompound) branching   (12)
3 (2) Spikelets 1-5-flowered, falling from rachis as a single unit while glumes remain attached to winged rachilla; culm base swollen into a bulb shape, enclosed by dark brown or brown leaf sheaths   (4)
+ Spikelets 3-8-flowered or more, rachilla remaining attached to rachis as glumes and nutlets fall with maturity; culm base not bulbous   (6)
4 (3) Spikelets 1-flowered; glumes inconspicuously veined.   58 C. monospermus
+ Spikelets 2-5-flowered; glumes conspicuously veined   (5)
5 (4) Spikelets narrowly ovoid, 3-5-flowered; glumes broadly ovate, densely brown puncticulate, 15-17-veined; nutlet obovoid to ellipsoid.   56 C. dubius
+ Spikelets ovoid-ellipsoid, 2- or 3-flowered; glumes ovate, brownish to straw-colored and laxly reddish puncticulate at base and apex, 9-13-veined; nutlet oblong.   57 C. hainanensis
6 (3) Spikelets 3- or 4-flowered; nutlet with spongy base of style extending downward along angles of nutlet.   19 C. cephalotes
+ Spikelets 8-flowered or more; nutlet without enlarged spongy apex   (7)
7 (6) Culms usually tall; spikelets several to more than 20, laxly fascicled; glumes conspicuously distichous, ca. 4 mm, apex obtuse and muticous   (8)
+ Culms dwarf; spikelets numerous, very densely arranged; glumes spirally imbricate or obscurely distichous, ca. 2 mm, apex recurved mucronate   (9)
8 (7) Leaves usually longer than culm; spikelets 5-8 mm, 6-10-flowered; nutlet oblong.   17 C. szechuanensis
+ Leaves usually shorter than culm; spikelets 7-25 mm, 8-48-flowered; nutlet obovoid.   18 C. niveus
9 (7) Spikelets ovoid to narrowly ovoid, 3-4 × ca. 1.5 mm; glumes spirally imbricate.   20 C. michelianus
+ Spikelets narrowly oblong-ovoid, oblong, or rarely narrowly ovoid, 3-8 × 1.5-2 mm; glumes distichous but sometimes obscurely so   (10)
10 (9) Spikelets very numerous, congested into capitulum, 4-5 mm; glumes oblong- lanceolate, apex slightly long mucronate; stigmas 2(or 3); nutlet narrowly oblong to oblong, nearly 3-sided.   21 C. pygmaeus
+ Spikelets many, congested with short or slightly elongate rays, 3-8 mm; glumes ovate or broadly ovate, apex shortly mucronate; stigmas 2; nutlet ellipsoid, plano-convex   (11)
11 (10) Inflorescences capitate, sometimes with 1 ray to 2 cm; glumes broadly ovate, white on both surfaces or rusty brown striate; nutlet oblong.   22 C. nipponicus
+ Inflorescence a simple anthela, with 3-6 rays to 6 cm; glumes ovate, pale on both surfaces but medially green; nutlet ellipsoid.   23 C. hilgendorfianus
12 (2) Nutlet lenticular, with face toward rachilla   (13)
+ Nutlet 3-sided (sometimes dorsiventrally compressed)   (15)
13 (12) Annuals; spikelets compressed, usually ca. 1.5 mm wide; glumes 1-2 mm; stamens 1 or 2, anthers ellipsoid.   61 C. limosus
+ Perennials; spikelets slightly turgid, (2.5-)3-5 mm wide; glumes 2.5-3 mm; stamens 3, anthers linear   (14)
14 (13) Culms 35-100 cm tall; leaf blade 3-10 mm wide; inflorescence a simple or compound anthela, usually with long rays and 5-17 spikelets arranged into spikes.   59 C. serotinus
+ Culms 4-20 cm tall; leaf blade ca. 1 cm wide; inflorescences capitate, usually with 1-8 spikelets.   60 C. pannonicus
15 (12) Perennial herbs; glumes ca. 2 mm; nutlet 0.7-1.5 mm   (16)
+ Annual or perennial herbs; glumes ca. 1(-1.5) mm; nutlet 0.2-0.3 mm   (23)
16 (15) Spikelets slightly turgid; glumes 7-veined or more   (17)
+ Spikelets compressed; glumes 3-5-veined   (19)
17 (16) Culms 1.5-5 cm tall; anthela rays much longer than culm.   6 C. radians
+ Culms 35-70 cm tall; anthela rays much shorter than culm   (18)
18 (17) Culms 3-angled but not winged; involucral bracts 6-12; inflorescence rays 6-16 cm.   4 C. diffusus
+ Culms 3-angled and winged; involucral bracts 3-5; inflorescence rays 2.5-5.5 cm.   5 C. trialatus
19 (16) Culms and rays with retrorse prickles.   7 C. surinamensis
+ Culms and rays smooth or with spreading or ascending prickles   (20)
20 (19) Culms compressed triquetrous, with leaves at basal part; leafy involucral bracts 5-12, unequal in length   (21)
+ Culms obtusely 3-angled to subterete, with bladeless sheaths basally; leafy involucral bracts 15-20, nearly equal in length   (22)
21 (20) Culms scabrid on angles; raylets present; stamens 3 per flower; nutlet compressed.   3 C. platystylis
+ Culms smooth; raylets absent; stamen 1 per flower; nutlet not compressed.   24 C. eragrostis
22 (20) Involucral bracts flexuose, drooping; apex of glumes acute; nutlet not stipitate.   1 C. involucratus
+ Involucral bracts rigid; apex of glumes acuminate; nutlet stipitate.   2 C. alternifolius
23 (15) Leaves very narrow, adaxially canaliculate, margin involute; glumes papery, apex truncate and with a recurved awn; nutlet oblong-obovoid to oblong   (24)
+ Leaves flat; glumes membranous, apex obtuse and mucronate or muticous; nutlet obovoid or ellipsoid   (25)
24 (23) Glumes with a (0.5-)0.6-1 mm awn; nutlets 0.5-0.6 mm.   15 C. cuspidatus
+ Glumes with a 0.2-0.5 mm awn; nutlets 0.7-0.9 mm.   16 C. castaneus
25 (23) Perennials or rarely annuals; culms with few leaves or with bladeless sheaths only; stamens (1-)3; nutlet less than 1/2 as long as subtending glume   (26)
+ Annuals without stolons (except C. duclouxii); culms usually leafy; stamens 1 or 2(or 3); nutlet 1/2 or more as long as subtending glume   (27)
26 (25) Leafy involucral bracts usually longer than inflorescence; glumes laxly imbricate, with recurved apex; anther apices not white setose; nutlet. 2-0.3 mm wide.   13 C. tenuispica
+ Leafy involucral bracts usually shorter than inflorescence; glumes densely imbricate, apex straight; anther apices white setose; nutlet 0.4-0.5 mm wide.   14 C. haspan
27 (25) Perennials, with stolons; culms scattered; spikelets 3-10, digitately arranged.   8 C. duclouxii
+ Annuals, with fibrous roots; culms tufted; spikelets many, congested into a capitulum or capitate heads   (28)
28 (27) Spikelets numerous, densely congested into a dense capitulum.   12 C. difformis
+ Spikelets (?solitary) several to more than 10, congested into a lax capitulum   (29)
29 (28) Glumes lax, orbicular-ovate to suborbicular, spreading when mature, apex mucronate.   9 C. nigrofuscus
+ Glumes slightly dense, broadly ovate or compressed orbicular, not spreading at maturity, apex muticous   (30)
30 (29) Spikelets ca. 1.5 mm wide; glumes broadly ovate, purplish brown to brown and yellowish green between both lateral veins.   10 C. fuscus
+ Spikelets ca. 1.8 mm wide; glumes ovate-lanceolate, blackish purple.   11 C. nanellus
31 (1) Rachilla not winged or only with very narrow white hyaline margins; style short   (32)
+ Rachilla winged; style usually long or medium, rarely short   (41)
32 (31) Perennials, with long stolons; spikelets slightly turgid; glumes abaxially not keeled or rarely keeled, margin involute, apex obtuse or rounded and usually muticous or rarely mucronate   (33)
+ Annuals, without rhizomes or stolons, with fibrous roots only; spikelets ± compressed; glumes abaxially keeled, margin not involute, apex mucronate to cuspidate   (36)
33 (32) Culms with long sheaths at basal part, sheaths with short blade or nearly bladeless; rachis of spikes glabrous; spikelets linear; glumes elliptic to oblong.   42 C. malaccensis
+ Culms with long blades; rachis of spikes hispidulous, rarely glabrous; spikelets narrowly ovoid; glumes ovate or broadly ovate   (34)
34 (33) Rachis of spikes laxly hispidulous, sometimes glabrous; spikelets ca. 3 mm wide; glumes obtuse and muticous at apex.   44 C. procerus
+ Rachis of spikes slightly densely hispidulous; spikelets 1.5-2.5 mm wide; glumes mucronate or muticous at apex   (35)
35 (34) Inflorescence a compound anthela; glumes with inconspicuous keel and not spinulose.   43 C. pilosus
+ Inflorescence a simple anthela; glumes with conspicuous keel and spinulose.   45 C. babakan
36 (32) Dried plants with odor like curry; stamen 1; glumes 7-9-veined, apex cuspidate.   53 C. squarrosus
+ Dried plants odorless; stamens 3; glumes 3-7-veined, apex obtuse, mucronulate, or cuspidate   (37)
37 (36) Rachis of spikes short; spikelets densely arranged, subcapitate; glumes densely imbricate; nutlet ca. 1/2 as long as subtending glume.   50 C. compressus
+ Rachis of spikes long; spikelets laxly arranged; glumes laxly imbricate; nutlet nearly as long as subtending glume   (38)
38 (37) Inflorescence a compound anthela; spikelets erect or obliquely spreading   (39)
+ Inflorescence a simple anthela; spikelets subspreading   (40)
39 (38) Rachilla not winged; glumes retuse and very shortly mucronate at apex; successive glumes 0.7-0.9 mm apart on same side of rachilla.   46 C. iria
+ Rachilla wings white hyaline and narrow; glumes orbicular and slightly long mucronate at apex; successive glumes 1-1.5 mm apart on same side of rachilla.   47 C. microiria
40 (38) Rachis glabrous; glumes reddish brown, apex slightly excurved mucronate.   48 C. amuricus
+ Rachis white hispidulous on angles; glumes dark blood-red, apex rounded and muticous.   49 C. orthostachyus
41 (31) Mature spikelets disarticulating at base of each glume, with each nutlet clasped by rachilla wings; rachilla wings yellowish spongy.   62 C. odoratus
+ Mature spikelets either falling as a unit or rachilla remaining attached to rachis and glumes falling; rachilla wings hyaline and not spongy   (42)
42 (41) Spikes ± cylindric, with numerous spikelets   (43)
+ Spikes broadly ovoid, turbinate, ellipsoid, oblong, orbicular, or rarely cylindric, with up to 10 spikelets (rarely more in C. glomeratus and C. eleusinoides)   (52)
43 (42) Mature spikelets not deciduous with glumes and nutlets falling from rachilla   (44)
+ Mature spikelets deciduous and falling from rachis with glumes and nutlets attached   (48)
44 (43) Spikelets linear, terete or subterete; rachilla broadly winged, wings lanceolate and ± deciduous   (45)
+ Spikelets narrowly oblong-ovoid, compressed; rachilla narrowly winged, wings linear and persistent   (46)
45 (44) Spikes broadly cylindric, 1.5-2 cm wide; spikelets spreading; anther connective minute.   25 C. digitatus
+ Spikes narrowly cylindric, 0.8-1.2 cm wide; spikelets ascending; anther connective prominent and subulate.   26 C. elatus
46 (44) Spikes ± pedunculate; spikelets ± distichous, laxly arranged; anthers linear.   27 C. exaltatus
+ Spikes not pedunculate; spikelets in several rows, densely arranged; anthers oblong   (47)
47 (46) Involucral bracts 8-15; anthela with 12-15 rays; spikes 1.5-11 cm; glumes oblong-obovate, 2.2-2.5 mm, apex straight mucronate; nutlet oblong to obovoid-oblong.   28 C. simaoensis
+ Involucral bracts 3-5; anthela with 6-10 rays; spikes 1.5-4 cm; glumes broadly ovate, ca. 1.5 mm, apex curved mucronate; nutlet obovoid to ellipsoid.   29 C. imbricatus
48 (43) Spikelets 1-3(or 4)-flowered; glumes tightly included around nutlet   (49)
+ Spikelets 4-10-flowered; glumes not tightly included around nutlet   (50)
49 (48) Spikes cylindric, (1-)2-3.5 × 0.6-1 cm, with parallel sides; anthers (0.6-)0.8-1 mm; nutlet ca. 0.5 mm wide; leaf blade margin smooth.   54 C. cyperoides
+ Spikes shortly cylindric, oblong, or ovoid, 1.2-1.8 × 0.8-1.2(-1.5) cm, with sides narrowed toward base; anthers 1-1.5 mm; nutlet 0.6-0.9 mm wide; leaf blade margin scabrous.   55 C. cyperinus
50 (48) Annuals; glumes with a recurved mucro at apex; stamens 1.   53 C. squarrosus
+ Perennials; glumes without mucro at apex; stamens 3   (51)
51 (50) Spikelets subulate, 5-18 mm, slightly less than 1 mm wide, arranged into a globose to half-globose spike; culms and anthela rays not papillose; nutlet linear-oblong; leaf sheath purplish red.   51 C. compactus
+ Spikelets narrowly oblong-ovoid, 4.5-7 × 1.8-2.5 mm, arranged into a cylindric spike; culms and anthela rays papillose; nutlet broadly ellipsoid to obovoid-ellipsoid; leaf sheath blackish brown.   52 C. javanicus
52 (42) Rhizomes short or surculose, without stolons or tubers; glumes laxly spreading   (53)
+ Rhizomes creeping or with stolons and tubers; glumes ± densely imbricate   (57)
53 (52) Culms slender; spikes broadly ovoid; spikelets subquadrangular, obliquely spreading to spreading at maturity; glumes ca. 4 mm.   37 C. tenuiculmis
+ Culms stout; spikes oblong, cylindric, ellipsoid, globose, or rarely broadly ovoid; spikelets slightly compressed, suberect or rarely spreading; glumes ca. 2 mm   (54)
54 (53) Spikelets laxly arranged, spreading after anthesis, 0.8-4 cm × ca. 1 mm; glumes dark blood-red.   38 C. distans
+ Spikelets densely or very densely arranged, suberect, not spreading after anthesis, 0.4-1.1 cm × 1.5-2 mm; glumes reddish brown or yellowish brown   (55)
55 (54) Annuals, without rhizomes but with fibrous roots; glumes muticous at apex.   41 C. glomeratus
+ Perennials; rhizomes short; glumes mucronate at apex   (56)
56 (55) Anthela raylets radially spreading; spikes 6 cm or more; spikelets 1-1.5 mm wide.   39 C. nutans
+ Anthela raylets suberect; spikes less than 6 cm; spikelets ca. 2 mm wide.   40 C. eleusinoides
57 (52) Culms stout; sheaths bladeless or apicalmost with short blade only; glumes oblong, concave, margin involute; spikelets slightly compressed, rachilla with reddish brown wings.   30 C. pangorei
+ Culms slightly slender; sheaths with blade; glumes ovate, broadly ovate, or ovate-elliptic, margin not involute   (58)
58 (57) Spikes ovoid; glumes laxly imbricate, spreading at maturity.   36 C. esculentus
+ Spikes broadly ovoid, obdeltoid, or obovoid; glumes densely imbricate, not spreading at maturity (laxly imbricate and spreading at maturity in C. mitis but spikes obovoid)   (59)
59 (58) Rachilla narrowly winged; glumes laxly imbricate, spreading at maturity; involucral bracts subulate, shorter than inflorescence.   35 C. mitis
+ Rachilla broadly winged; glumes densely imbricate, not spreading at maturity; involucral bracts leaflike, usually longer than inflorescence   (60)
60 (59) Leaves and involucral bracts slightly narrow, usually plicate; anthela rays erect or suberect, less than 2 cm   (61)
+ Leaves and involucral bracts slightly broad, usually flat; anthela rays obliquely spreading, slender, mostly to 12 cm   (62)
61 (60) Stolons short; culms laxly tufted; rays of anthelae erect; spikelets laxly arranged into spikes, linear, ca. 1 mm wide; anthers ellipsoid; nutlet oblong.   31 C. linearispiculatus
+ Stolons long; culms scattered; rays of anthelae slightly obliquely spreading; spikelets nearly digitately arranged at apex of ray, oblong-lanceolate to lanceolate, 2-3 mm wide, slightly turgid; anthers linear; nutlet obovoid to ellipsoid.   32 C. stoloniferus
62 (60) Glumes dark blood-red, ovate to oblong-ovate.   33 C. rotundus
+ Glumes straw-colored to brownish yellow, broadly ovate to elliptic.   34 C. tuberosus

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