| # The grass genera of the world |

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

### Glyceria R.Br.

From the Greek glykeros (sweet), referring to the seeds of G. fluitans and perhaps the leaves and roots of some other species.

Sweetgrass.

Type species: Type: G. fluitans (L.) R.Br.

Including Devauxia Kunth, Exydra Endl., Heleochloa Fries, Hemibromus Steud., Hydrochloa Hartm., Hydropoa (Dumort.) Dumort., Nevroloma Raf., Plotia Steud., Porroteranthe Steud.

Habit, vegetative morphology. Glabrous, perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 25–200 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal, or not basally aggregated; non-auriculate. Sheath margins joined. Leaf blades linear; apically flat; broad, or narrow; 1.5–18 mm wide; flat, or folded; cross veined, or without cross venation (when narrower); persistent; once-folded in bud. Ligule an unfringed membrane; not truncate.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding and inbreeding.

Inflorescence. Inflorescence paniculate (usually), or a single raceme (rarely); open. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets secund, or not secund.

Female-fertile spikelets. Spikelets 2–35 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent. Callus short; blunt.

Glumes two; very unequal to more or less equal; nearly always shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed; awnless; non-carinate; similar (herbaceous). Lower glume 1(–3) nerved. Upper glume 1(–5) nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 3–16. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous to thinly leathery); not becoming indurated; entire, or incised; when entire pointed, or blunt; when incised, 3 lobed, or 5 lobed; not deeply cleft (toothed); awnless; hairless; carinate, or non-carinate (then rounded on the back); (5–)7(–11) nerved; with the nerves non-confluent. Palea present; relatively long; entire to apically notched; awnless, without apical setae, or with apical setae; thinner than the lemma; not indurated (membranous); 2-nerved; 2-keeled. Palea keels sometimes, slightly winged, or wingless. Lodicules present; joined, or joined to free; fleshy; glabrous; toothed, or not toothed. Stamens 2, or 3. Anthers 0.3–3 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved, or not grooved; compressed dorsiventrally. Hilum long-linear. Embryo small; not waisted. Endosperm hard; without lipid; containing compound starch grains. 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; 3 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present, or absent. Intercostal papillae over-arching the stomata, or not over-arching the stomata; consisting of one oblique swelling per cell. Long-cells similar in shape costally and intercostally, or markedly different in shape costally and intercostally (the costals often fusiform); of similar wall thickness costally and intercostally. Intercostal zones with typical long-cells, or exhibiting many atypical long-cells (G. australis having many short long-cells). Mid-intercostal long-cells rectangular; having straight or only gently undulating walls. Microhairs absent. Stomata common; 24–36 microns long. Subsidiaries low dome-shaped, or parallel-sided, or parallel-sided and dome-shaped. Guard-cells overlapped by the interstomatals (at least in G. australis). Intercostal short-cells common, or absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without fusoids (but at least sometimes with large cavities). Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous to not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (sometimes restricted to midrib ‘hinges’); when grouped, in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent; forming ‘figures’ (e.g. G. australis), or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in one or two rings.

Cytology. Chromosome base number, x = 10. 2n = 20, 28, 40, 56, and 60. 2, 4, and 6 ploid (and aneuploids). Chromosomes ‘small to medium sized’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Meliceae. 40 species.

Distribution, phytogeography, ecology. Cosmopolitan.

Commonly adventive. Hydrophytic to helophytic; glycophytic.

Economic aspects. Important native pasture species: in swampy places, G. elata, G. grandis, G. maxima, G. pauciflora, G. striata.

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

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - G. australis C.E. Hubb., G. septentionalis Hitchc.

Illustrations. • Glyceria maxima (as G. aquatica), general aspect: Eng. Bot. (1872). • Glyceria fluitans, general aspect: Eng. Bot. (1872). • Glyceria fluitans, general aspect: J. Curtis, 1824. • cf. Glyceria notata (as G. plicata): Eng. Bot. (1872). • Glyceria australis, inflorescence and spikelet. • Lemma tip of Glyceria declinata. Glyceria declinata. Blunt-erose lemma tip, nerves non-confluent. • Glyceria declinata, flower details with pollen on stigmas: this project. Glyceria declinata. Fleshy, joined lodicules, and winged palea keels. Pollen on stigmas. • Glyceria plicata: Bor, Flora of Iraq (1968). • Spikelet of Glyceria plicata. • Palea and flower of Glyceria plicata. • Palea of Glyceria plicata. • Winged palea back of Glyceria declinata. Glyceria declinata. Keel-winged palea back. • Glyceria declinata, partially dissected floret - lodicules, etc.. Glyceria declinata. Lemma removed, showing two joined, fleshy lodicules and developing fruit, inside a palea with two winged keels. • Young ovary and lodicules of Glyeria declinata. Glyceria declinata. Young ovary and fleshy, joined lodicules.

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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