The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 5–15 cm high; herbaceous; unbranched above. Leaves non-auriculate. Sheath margins free. Leaf blades narrow; 1–2 mm wide; sagittate (e.g. S. appendiculata), or not cordate, not sagittate; not setaceous (convolute or flat); flat, or rolled (convolute); without cross venation. Ligule an unfringed membrane; not truncate; 0.5 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 bractlike scales at the base of the inflorescence); overtly heteromorphic.
Inflorescence. Inflorescence paniculate; contracted; capitate, or more or less ovoid; 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 compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.
Glumes two; more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; pointed; shortly awned, or awnless (then mucronate); carinate; similar (ovate, membranous). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 3–4. Lemmas decidedly firmer than the glumes (silvery or grey); not becoming indurated; incised; not deeply cleft (toothed); awnless, or mucronate (the teeth shortly aristulate); hairy (proximally); carinate; without a germination flap; 5 nerved. Palea present; relatively long; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit small (about 1.5 mm long). Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells costal long-cells smaller; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs (and solitary); silicified (a few only), or not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (many paired). Costal silica bodies horizontally-elongated crenate/sinuous (often short), or rounded (often irregular, integrading with the sinuous/crenate forms); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or nodular in section; with the ribs more or less constant in size. Midrib conspicuous (by the larger bundle); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (bulliforms not apparent). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (Is). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Seslerieae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Sesleriinae. 2 species.
Distribution, phytogeography, ecology. Central and southern Europe.
References, etc. Leaf anatomical: studied by us - S. (Sesleria) sphaerocephala.