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The grass genera of the world

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

Sesleria Scop.

Including Diptychum Dulac

Excluding Oreochloa, Psilathera, Sesleriella

Habit, vegetative morphology. Perennial; usually caespitose. Culms 10–70 cm high; herbaceous; usually unbranched above. Leaves non-auriculate. Sheath margins joined. Leaf blades linear; narrow; 0.4–6 mm wide; flat, or folded, or rolled (convolute); without cross venation; persistent. Ligule an unfringed membrane; truncate, or not truncate; 0.1–1 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (the sterile spikelets reduced to a pair (usually) of bractlike scales (representing their glumes?) at the base of the inflorescence); overtly heteromorphic.

Inflorescence. Inflorescence paniculate; contracted (often bluish, greyish or whitish); more or less ovoid, or spicate, or more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.

Female-sterile spikelets. The sterile spikelets vestigial, represented by bracts at the base of the inflorescence.

Female-fertile spikelets. Spikelets 3.5–9 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless. Hairy callus absent.

Glumes two; more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas (rarely); pointed (acuminate); shortly awned, or awnless; carinate; similar (membranous). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 2–6. Lemmas similar in texture to the glumes (membranous); not becoming indurated; incised; 2–5 lobed; not deeply cleft (with 2–5 teeth); mucronate to awned (the teeth usually aristulate). Awns when present, 1, or 3, or 5; median, or median and lateral; the median similar in form to the laterals (when laterals present); apical; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma. The lateral awns when present, shorter than the median. Lemmas hairy, or hairless; non-carinate; 3–5 nerved. Palea present; relatively long; awnless, without apical setae, or with apical setae, or awned; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Anthers 2.5–4 mm long; not penicillate. Ovary apically hairy. Styles fused. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally; hairy on the body. Hilum short. Embryo small; not waisted. Endosperm hard; without lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Seedling with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 3 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common, or absent or very rare; not paired. Costal short-cells predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; seemingly without adaxial palisade (but see Metcalfe 1960). Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (sometimes Ammophila-type, or confined to ‘midrib hinges’); sometimes in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles, or not all bundle-associated (rarely).

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 7. 2n = 14 (rarely), or 28, or 42, or 56. 2 ploid (rarely), or 4 ploid, or 6 ploid, or 8 ploid (often 2n = 56). Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Seslerieae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Sesleriinae. 25 species.

Distribution, phytogeography, ecology. Europe, western Asia.

Mesophytic, or xerophytic; species of open habitats. Uplands and mountain rocks.

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

References, etc. Morphological/taxonomic: Deyl 1946. Leaf anatomical: Metcalfe 1960; studied by us - S. caerulea (L.) Ard.

Illustrations. • S. autumnalis, as S. elongata: P. Beauv. (1812). • S. caerulea: Lamson-Scribner (1890). • S. caerulea, 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: 11th December 2017.’.