The grass genera of the world
Type species: Type: L. ovatus L.
Including Avena Scop.
Habit, vegetative morphology. Slender annual; caespitose. Culms 8–50(–60) cm high; herbaceous; unbranched above. Culm nodes hairy, or glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear-lanceolate; apically flat; narrow; 1.5–10 mm wide; not setaceous (pubescent); flat; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane, or a fringed membrane (rarely); irregularly truncate; 2.5–3 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; inbreeding.
Inflorescence. Inflorescence paniculate; contracted; more or less ovoid (silky-white hairy and bristly). Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 5–10 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension naked. Hairy callus absent. Callus blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairy (villous); pointed; awned; non-carinate; similar (narrowly lanceolate, membranous, hairy, tapering into fine bristles, thinly membranous). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous); not becoming indurated; incised; 2 lobed (narrowed into 2 awn-tipped teeth); not deeply cleft; awned. Awns 3; median and lateral (with two short terminal laterals in addition to the longer median); the median different in form from the laterals; dorsal; from near the top, or from well down the back; geniculate; hairless; much longer than the body of the lemma; entered by one vein. The lateral awns shorter than the median (terminal, straight). Lemmas hairy, or hairless; non-carinate; 5 nerved. Palea present; relatively long (but shorter than the lemma); apically notched; awnless, without apical setae; not indurated (thin); 2-nerved; 2-keeled, or keel-less. Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 1.5–2 mm long; not penicillate. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small. Hilum short. Embryo small; not waisted. Endosperm liquid in the mature fruit; with lipid.
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 to fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 37–45 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare; in cork/silica-cell pairs, or not paired (solitaries, and pairs adjacent to the prickles); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies horizontally-elongated smooth (predominating), or rounded.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (ill defined, in material seen). 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 one or two rings.
Phytochemistry. Tissues of the culm bases with little or no starch.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Aveninae. 1 species (L. ovatus).
Distribution, phytogeography, ecology. Mediterranean.
Commonly adventive. Xerophytic; species of open habitats. Especially maritime sands.
Economic aspects. Significant weed species: L. ovatus. Cultivated as an ornamental.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia coronata and Puccinia hordei.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us.
Illustrations. • L. ovatus: Gardner, 1952. • General aspect (L. ovatus): Gibbs Russell et al., 1990. • L. ovatus, general aspect: Eng. Bot. (1872). • Spikelets in close-up (L. ovatus)
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. delta-intkey.com/grass’.