| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Calamagrostis Adans.

From the Greek kalamos (a reed) and agrostis (a kind of grass), the type species being a reedy grass.

Type species: Type: Arundo calamagrostis L.

Including Achaeta Fourn., Amagris Raf., Ancistrochloa Honda, Anisachne Keng, Athernotus Dulac, Chamaecalamus Meyen, Cinnagrostis Griseb., Pteropodium Steud., Sclerodeuxia Pilger

Excluding Aniselytron, Deyeuxia, Dichelachne, Stilpnophleum

Habit, vegetative morphology. Perennial (some species reedlike); rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–200 cm high; herbaceous; branched above, or unbranched above (commonly). Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 1–15 mm wide; setaceous, or not setaceous; flat (usually), or rolled (convolute); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane (sometimes erose-ciliate); truncate, or not truncate; 1–12 mm long. Contra-ligule present (a membrane), or absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding; exposed-cleistogamous, or chasmogamous. Apomictic (pseudogamous or non-pseudogamous), or reproducing sexually.

Inflorescence. Inflorescence paniculate; open (rarely), or contracted; when contracted capitate to spicate, or more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 3–7(–8) mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; hairy; the rachilla extension (when present) naked. Hairy callus present (the hairs surrounding and often as long as or much exceeding the lemma). Callus hairs present, more than 0.5 mm long.

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas (the lemma only about 1/2–2/3 as long); pointed (acute to acuminate); awnless; carinate; similar. Lower glume 1 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas less firm than the glumes to similar in texture to the glumes (usually hyaline); not becoming indurated; incised; not deeply cleft (emarginate, bilobed or irregularly denticulate); awned. Awns 1; median; from a sinus, or dorsal; when dorsal, from well down the back; non-geniculate, or geniculate; much shorter than the body of the lemma to about as long as the body of the lemma, or much longer than the body of the lemma; entered by one vein. Lemmas hairless; non-carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; entire, or apically notched (via excurrent veins); awnless, without apical setae; textured like the lemma; not indurated (thin); 2-nerved; 2-keeled, or keel-less. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers 1–4 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small. Hilum long-linear. Embryo small; not waisted. Endosperm liquid in the mature fruit, or hard; with lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Seedling with a long mesocotyl; with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 1 veined, or 3 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common. Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (sometimes), or not paired (but often paired with a prickle or hook); silicified (rarely), or not silicified (usually). Intercostal silica bodies when present, tall-and-narrow. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or ‘panicoid-type’; when ‘panicoid type’, nodular.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles (C. epigejos exhibits a large median with a small lateral on either side). Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in three or more rings.

Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly long-chain. Leaves without flavonoid sulphates (2 species).

Cytology. Chromosome base number, x = 7. 2n = 28, 42, and 56, or 56–91. 4, 6, and 8 ploid (lowest 2n=28?), or 8–13 ploid. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. About 230 species.

Distribution, phytogeography, ecology. Temperate.

Commonly adventive. Mostly helophytic to mesophytic; shade species to species of open habitats; glycophytic, or halophytic (rarely). Diverse habitats, including coastal sand - see ×Ammocalamagrostis.

Economic aspects. Important native pasture species: C. canadensis, C. inexpansa, C. rubescens, C. montanensis etc. ×Ammocalamagrostis is a useful sandbinder.

Hybrids. Intergeneric hybrids with Agrostis. C. epigejos hybridizes with Ammophila arenaria (×Ammocalamagrostis P. Fourn.; ×Calamophila O. Schwartz = ×Ammocalamagrostis, ×Calammophila Brand = ×Ammocalamagrostis).

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, Puccinia pygmaea, Puccinia brachypodii, Puccinia poarum, and Puccinia recondita. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Entyloma and Urocystis. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - C. epigejos (L.) Roth.

Illustrations. • Calamagrostis epigejos, general aspect: Eng. Bot. (1872). • C. epigejos, general aspect. • Calamagrostis canescens (as lanceolata), general aspect: Eng. Bot. (1872). • Calamagrostis pseudophragmites: Bor, Flora of Iraq (1968). • cf. Calamagrostis setifolia (as Deyeuxia): Hooker, Fl. Novae-Zelandiae (1853). • Calamagrostis sclerophylla (as Deyeuxia): Hook. Ic. Pl. 27 (1901). • Calamagrostis stricta: general aspect: Eng. Bot. (1872). • C. stricta var. hookeri: general aspect: Eng. Bot. (1872).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 15th June 2025. delta-intkey.com’.

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