The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous. Culms herbaceous. Leaves non-auriculate. Sheath margins free. Leaf blades not pseudopetiolate; without cross venation. Ligule an unfringed membrane; truncate; 4–5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a single raceme (lax); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (nodding to one side); shortly pedicellate; not imbricate.
Female-fertile spikelets. Spikelets 15–20 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus blunt.
Glumes two; very unequal; shorter than the adjacent lemmas; pointed (acute); awnless; similar (papery). Lower glume 5 nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 3–4; clearly specialised and modified in form (forming a narrowly lanceolate cluster).
Female-fertile florets 2. Lemmas decidedly firmer than the glumes (leathery); not becoming indurated; incised; 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; dorsal; from near the top (or at about 1/3 the way down); geniculate. Lemmas hairy; non-carinate; without a germination flap; 7–11 nerved (and ribbed). Palea present; 2-nerved. Lodicules present; 2; joined; fleshy; not toothed; not or scarcely vascularized. Ovary apically glabrous (?); without a conspicuous apical appendage (?). Stigmas 2 (?).
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized (5–8 mm long). Hilum long-linear. Embryo small. Endosperm hard; without lipid.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones exhibiting many atypical long-cells (some tending to be hexagonal). Mid-intercostal long-cells having markedly sinuous walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; not paired; silicified. Intercostal silica bodies tall-and-narrow (elliptical). Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired (mostly in short or long rows, some solitary). Costal silica bodies panicoid-type; mostly nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs to adaxially flat (the abaxial ribs more conspicuous); with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Plant and inflorescence not as in Lygeum (q.v.).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Meliceae. 1 species (L. avenacea).
Distribution, phytogeography, ecology. Lebanon.
Xerophytic (among rocks).
References, etc. Leaf anatomical: Metcalfe 1960.
Illustrations. • L. avenacea: Thiebaut, Fl. Labano-Syrienne (1953)
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’.