The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose (with short rhizomes). Culms 30–100 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins joined. Leaf blades linear; narrow; 1–4 mm wide; flat, or rolled (convolute); without cross venation; rolled in bud. Ligule present; an unfringed membrane; truncate (at back); 0.5–3 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted; paniculate; open (up to 10 cm). Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets secund (in the lax panicle); long pedicellate.
Female-fertile spikelets. Spikelets 9–25 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present (long-pilose). Callus short; blunt.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; pointed (acute); awnless; carinate, or non-carinate; similar (membranous, ovate-lanceolate). Lower glume (1–)3 nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1–2; merely underdeveloped.
Female-fertile florets 3–7. Lemmas decidedly firmer than the glumes (becoming leathery); not becoming indurated; incised; 2 lobed; not deeply cleft (incised to about 1/4); awned. Awns 1; median; dorsal; from near the top (behind the sinus); hairless; about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairless; carinate to non-carinate; without a germination flap; 7–13 nerved. Palea present; relatively long, or conspicuous but relatively short, or very reduced; not indurated (membranous); 2-nerved; 2-keeled. Palea keels hairy (ciiate above). Lodicules present; 2; joined to free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 1–2 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized (about 4 mm long); not grooved. Hilum long-linear. Embryo small. 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.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar 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; not paired; not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous (a few), or panicoid-type; mostly elongated, iregularly nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade nodular in section; with the ribs more or less constant in size. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid. Chromosomes small.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Meliceae. 1 species.
Distribution, phytogeography, ecology. North Eurasia, Japan, North America.
Mesophytic; shade species. In woods.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia coronata.
References, etc. Leaf anatomical: this project.
Illustrations. • S. purpurascens: Hitchcock and Chase (1950)
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: 13th November 2017. delta-intkey.com/grass’.