Herbs, annual or perennial, rhizomatous to stoloniferous. Culms (stems) simple, often 3-sided. Leaves basal and/or cauline, often 3-ranked, comprising a blade and sheath but sometimes only sheath present; sheath open or closed; ligule often present, sometimes on opposite side to leaf blade; leaf blade usually linear, grasslike, sometimes basally broader and constricted into a pseudopetiole. Involucral bracts 1 to several, leaflike or glumelike. Inflorescences unbranched and spicate or capitate, to branched and anthelate (umbel-like) or paniculate, comprising 1 to many ultimate inflorescence units, these either indeterminate and called spikelets or in a few genera determinate and called pseudospikelets (see explanation below). Spikelets with 1 to many glumes, sometimes reduced to a single flower and aggregated into unisexual spikes; glumes membranous to leathery, spirally arranged or 2-ranked, each subtending a single flower. Pseudospikelets comprising 2-12 membranous scalelike floral bracts on a much reduced axis; lowest 2 bracts opposite, keeled, pseudospikelet subtended and usually hidden by a glumelike bract; bracts spirally arranged and aggregated into spikeletlike spikes. Flowers bisexual or unisexual with plants monoecious or rarely dioecious. Perianth absent or reduced to bristles or scales. Stamens 1-3; anthers basifixed. Ovary 2- or 3-carpellate, unilocular, with a single ovule; style divided or rarely undivided, base sometimes persistent and variously shaped in fruit; stigmas 2 or 3. Fruit usually a hard 2- or 3-sided nutlet, rarely with a succulent or corky exocarp, surface smooth or variously minutely patterned, sometimes partially or completely enclosed by an enlarged basal prophyll (utricle).

Recent phylogenetic studies (e.g., D. A. Simpson et al., Aliso 23: 72-83. 2007; A. M. Muasya et al., Bot. Rev. (Lancaster) 75: 52-66. 2009) suggest that tribal and generic delimitation in Cyperaceae is likely to be modified in the future.

The closest relatives to Cyperaceae are Juncaceae and Thurniaceae (D. A. Simpson in P. Rudall, P. J. Cribb, D. F. Cutler & C. J. Humphries, eds., Monocot. Syst. Evol. 2: 497-509. 1995) in the order Poales. Poaceae, which shares some characteristics of Cyperaceae, such as wind pollination and reduced floral structure, has often been placed near to Cyperaceae but is now shown to be more distantly related (H. P. Linder & E. A. Kellogg in P. Rudall et al., loc. cit.: 473-496; D. A. Simpson in P. Rudall et al., loc. cit.: 497-509).

Inflorescence structure in Cyperaceae is notoriously difficult to interpret due to its highly reduced nature. Consequently, the terminology used in describing parts of the inflorescence can be confusing with several terms often being applied to the same structure. In addition, several terms are also used in the Poaceae, but they do not always relate to the same structure in both families. A laudable attempt to standardize terminology in Cyperaceae was made by I. Kukkonen (Ann. Bot. Fenn. 31: 37-43. 1994). In our treatment we have attempted to keep terminology as simple as possible.

Inflorescences are generally either unbranched or very shortly branched and spicate or capitate in appearance to prominently branched and paniculate or anthelate (umbel-like), with variations around these. The basic unit of the inflorescence in most Cyperaceae is the spikelet. This comprises a very short to elongated axis, which subtends one to many scalelike bracts, referred to here as glumes. Each glume subtends and partially hides a single very small, bisexual or unisexual flower, which may or may not have a perianth. The perianth, when present, is reduced to bristles or scales. There may be 1-3 stamens and a pistil comprising an ovary, style, and 2 or 3 stigmas. The ovary gives rise to a hard, 1-seeded nutlet (sometimes referred to as an achene). Spikelets tend to be aggregated into larger structures known as spikes. In the tribe Cariceae this basic structure is modified such that the spikelet is reduced to a single flower that is enclosed by a saclike structure known as a utricle, the latter being a modified prophyll at the base of the spikelet. The utricle is subtended by a glumelike bract, and the whole structure is again aggregated with others into spikes. Some confusion arises with caricoid spikes especially as the spikelets comprise only one flower and are subtended by a glumelike bract. This has meant that spikes are sometimes referred to as spikelets and the glumelike bracts as true glumes.

The spikelet is indeterminate, i.e., having no terminal flower. However, in Hypolytrum, Lepironia, and Mapania, the basic inflorescence unit has an apparently terminal female flower. To distinguish this type of unit, the term pseudospikelet is used here; some authors refer to it as a spicoid. Its structure is rather different to that of the spikelet, comprising 2-12 scalelike floral bracts on a very much reduced axis. The two lowest bracts are opposite, keeled, and often enclose the upper bracts (when the latter are present). The lower bracts subtend a male flower comprising a single stamen, the upper bracts usually being empty. The terminal flower, which is not subtended by a floral bract, is female. There are no perianth bristles or scales, and the whole structure is subtended and partially to fully hidden by a glumelike bract. These are again aggregated into spikes, but there is further confusion in terminology with the spikes sometimes being referred to as spikelets. The above interpretation of the pseudospikelet is widely accepted, although some workers have interpreted it as a single flower.

One of us (Dai) believes that if Kyllinga and Pycreus are treated as separate genera from Cyperus, as they are in this treatment, then Juncellus and Mariscus should also be separated from Cyperus on account of their distinct morphological characters.

Tang Tsin & Wang Fa-Tsuan. 1961. Cyperaceae (1). In: Tang Tsin & Wang Fa-Tsuan, eds., Fl. Reipubl. Popularis Sin. 11: i-xv, 1-261; Liang Song-yun, Dai Lun-kai, Tang Yan-cheng & Li Pei-chun. 2000. Cyperaceae (2). In: Dai Lun-kai & Liang Song-yun, eds., Fl. Reipubl. Popularis Sin. 12: i-xxii, 1-582.

For accurate identification of Cyperaceae good fruiting material should be used wherever possible. Indeed this is essential in certain genera, such as Fimbristylis and Scleria. It is also important to have underground parts as these may be diagnostic for some species. Care is needed when counting the number of stigmas as these are easily broken off. Several should be observed from the same specimen. Care is also needed when counting the stamens. Anthers break off easily leaving the filaments partially hidden within the glumes. Always check that filaments are present. Also, care should be taken to distinguish perianth bristles from filaments as the number of perianth bristles may be useful in separating taxa. The bristles will usually have antrorse or retrorse hairs on them.

Glossary

Within the definitions, italics indicate terms that are defined in this glossary.

Amphicarpous - applied to a small secondary inflorescence occurring at the base of the culm in certain genera, particularly Schoenoplectus.

Androgynous - having male and female flowers in the same structure such as a spike in Carex.

Anthela (plural anthelae, adjective anthelate) - an umbel-like inflorescence in which the primary branches ± arise from the same point, the inflorescence being subtended by 1 to several involucral bracts.

Beak - short extension at the apex of a utricle or nutlet.

Biconvex - 2-sided, the sides convex.

Cancellate - having the appearance of a lattice.

Capitate - headlike inflorescence, without any apparent branching.

Cladoprophyll - a sterile utricle found at the base of a Carex spike.

Compound - applied to an inflorescence or partial inflorescence where there are 2 orders of branching, i.e., primary and secondary.

Compressed trigonous - 3-sided, but distinctly flattened and thus appearing to be 2-sided.

Conic - cone-shaped, being wider at the base than the apex; here it is used as the 3-dimensional equivalent of lanceolate.

Contraligule - membranous, ligulelike structure at the apex of the leaf sheath on the side of the culm facing away from the leaf blade.

Culm - stem supporting the inflorescence.

Decompound - applied to an inflorescence or partial inflorescence where there are 3 or more orders of branching, i.e., primary, secondary, and tertiary.

Determinate - applied to an inflorescence with terminal flowers and therefore not capable of indefinite growth.

Disk - 3-lobed structure occurring at the base of the nutlet in Scleria and Diplacrum. In some species it may be indistinct, whereas in Scleria sumatrensis it is developed into a cuplike structure ± covering the nutlet.

Distichous (of glumes and spikelets) - arranged in 2 opposite rows down the rachilla or rachis.

Glume - membranous to leathery scalelike structure subtending individual flowers.

Gynophore - short stalk at the base of a nutlet.

Indeterminate - inflorescence which, in theory, is capable of indefinite growth.

Involucral bract - bract or bracts occurring at the point where the inflorescence arises from the culm. Vary from being leaflike to glumelike or setaceous.

Isodiametric - of equal size both horizontally and vertically.

Keel - used here for the midrib of a glume or scalelike bract.

Lageniform - urn-shaped with a constriction in the middle.

Ligule - membranous tissue or fringe of hairs occurring at the apex of the leaf sheath on the inner side at the point where it joins the leaf blade.

Nutlet - hardened, usually minute, 1-seeded fruit, the surface of which may be smooth to variously patterned and a diagnostic character for many species. Often called an achene in literature on Cyperaceae.

Paniculate - inflorescence comprising partial inflorescences arising at intervals along the main inflorescence axis.

Partial inflorescence - primary branches of an inflorescence.

Perianth bristles - small bristlelike or scalelike structures at the base of the nutlet. Presumed to be the remnants of a fully developed perianth.

Prophyll - 2-keeled structure at the base of a branch within an inflorescence. It may be glumelike or tubular or, in Kobresia and Carex, developed into a utricle.

Pseudospikelet - the ultimate inflorescence unit in Hypolytrum, Lepironia, and Mapania. Has a much reduced axis and appears flowerlike. Comprises 2-12 scalelike bracts each subtending a male flower. The whole structure is terminated by a female flower, thus making it determinate.

Rachis - the axis of a spike.

Rachilla - the axis of a spikelet.

Ray - branches of an anthela.

Rhizome - underground stem, which may be short, often giving the plant a tufted habit, or long creeping.

Scalelike bract - membranous scalelike structure in a pseudospikelet each of which subtends a male flower comprising a single stamen only. The lowest 2 floral bracts usually have a keel and are opposite.

Scrobiculate - having numerous minute pits or depressions.

Septate - partitioned. In some species, particularly in Eleocharis, the culm has a series of horizontal septa, which are best seen in dried material.

Simple - applied to an inflorescence or partial inflorescence where there is only one order of branching, i.e., primary branching

Spike - an aggregation of spikelets or pseudospikelets; sometimes the whole structure is similar in appearance to a spikelet (in Ascolepis Nees ex Steudel, Carex, Hypolytrum, Kobresia, Lepironia, Lipocarpha, and Mapania).

Spikelet - the ultimate inflorescence unit in most genera of Cyperaceae. Has an elongated or reduced axis with 1 to many glumes, each glume subtending a bisexual or unisexual flower.

Squarrose - with tips spreading outward. In Cyperaceae usually applied to the apex of the glumes.

Stipe - short, narrowed extension to the base of the nutlet.

Stolon - in Cyperaceae this term is applied to a thin underground branch arising from the rhizome or base of the culm. Each stolon terminates in an aerial shoot.

Style base - a variously shaped portion at the base of the style which is persistent on the mature nutlet in some genera.

Trabeculate - having the appearance of minute girders.

Trigonous - 3-sided, with the margins blunt and rounded. Applied here to the culm and nutlet.

Triquetrous - 3-sided with the margins acute. Applied here to the culm and nutlet.

Utricle - a prophyll which has developed into a characteristic bottlelike structure and partially to completely surrounds the nutlet in Kobresia and Carex.

Systematic list of subfamilies, tribes, and genera

The Cyperaceae are the third largest family in the Monocotyledons (after Orchidaceae and Poaceae). The largest genera in China are Carex (527 spp.), Cyperus (62 spp.), Fimbristylis (53 spp.), Eleocharis (35 spp.), and Scleria (24 spp.). In the present treatment we follow D. A. Simpson (Amer. J. Bot. 90: 1071-1087. 2003) for subfamily delimitation and Goetghebeur (in K. Kubitzki, Fam. Gen. Vasc. Pl. 4: 141-190. 1998) for tribal and generic delimitation and sequence. Two subfamilies and eight tribes of Cyperaceae occur in China with generic allocation as follows:

1. MAPANIOIDEAE

1. Hypolytreae
1. Hypolytrum (p. 168)
2. Mapania (p. 169)
3. Lepironia (p. 170)

2. CYPEROIDEAE

2. Scirpeae
4. Scirpus (p. 171)
5. Eriophorum (p. 174)
6. Trichophorum (p. 176)
7. Fuirena (p. 178)
8. Bolboschoenus (p. 179)
9. Actinoscirpus (p. 181)
10. Schoenoplectus (p. 181)
11. Eleocharis (p. 188)

3. Abildgaardieae
12. Fimbristylis (p. 200)
13. Bulbostylis (p. 218)

4. Cypereae
14. Isolepis (p. 219)
15. Cyperus (p. 219)
16. Courtoisina (p. 241)
17. Remirea (p. 241)
18. Pycreus (p. 242)
19. Kyllinga (p. 246)
20. Lipocarpha (p. 249)

5. Dulichieae
21. Blysmus (p. 251)

6. Schoeneae
22. Actinoschoenus (p. 252)
23. Rhynchospora (p. 253)
24. Schoenus (p. 256)
25. Gahnia (p. 257)
26. Cladium (p. 258)
27. Machaerina (p. 259)
28. Lepidosperma (p. 260)
29. Tricostularia (p. 260)

7. Sclerieae
30. Scleria (p. 260)
31. Diplacrum (p. 268)

8. Cariceae
32. Kobresia (p. 269)
33. Carex (p. 285)

One hundred and six genera and ca. 5,400 species: worldwide except Antarctica; 33 genera and 865 species (326 endemic, five introduced) in China.

(Authors: Dai Lunkai (戴伦凯)[62], Liang Songyun (梁松筠 Liang Song-jun)1, Zhang Shuren (张树仁)1, Tang Yancheng (汤彦承 Tang Yen-cheng)1; Tetsuo Koyama[63], Gordon C. Tucker[64], David A. Simpson[65], Henry J. Noltie[66], Mark T. Strong[67], Jeremy J. Bruhl[68], Karen L. Wilson[69], A. Muthama Muasya[70])