The grass genera of the world
Including Costia Willkom, Douglasdeweya, Kratzmannia Opiz
Excluding Elymus, Leymus, Elytrigia, Australopyrum, Pascopyrum etc.
Habit, vegetative morphology. Perennial; rhizomatous, or caespitose. Culms 15–150 cm high; herbaceous; unbranched above; tuberous, or not tuberous. Culm nodes hairy, or glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades linear; narrow; 1.2–10 mm wide; not setaceous; flat, or rolled (convolute); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule present; an unfringed membrane; truncate (or very short); 0.1–1 mm long (leathery to membranous). Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence a single spike (usually pectinate). Rachides hollowed, or flattened, or winged, or neither flattened nor hollowed, not winged. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (diverging from the rachis); not secund; distichous (in rows); pedicellate; imbricate.
Female-fertile spikelets. Spikelets 6–12(–15) mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless (shortly pilose to scabrous). Hairy callus present, or absent. Callus very short; blunt.
Glumes two; more or less equal; shorter than the adjacent lemmas; lateral to the rachis; hairy (pilose), or hairless; when hairless, glabrous; pointed; not subulate; awned (the awn to 3 mm long), or awnless; carinate (usually strongly keeled); similar (lanceolate ovate, somewhat asymmetric). Lower glume 2–5 nerved. Upper glume 2–5 nerved. Spikelets with female-fertile florets only (rarely), or with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 3–8 (rarely two, or up to ten). Lemmas similar in texture to the glumes (leathery); not becoming indurated; entire; pointed; awnless, or mucronate, or awned. Awns when present, 1; apical; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma (rarely more than 5 mm long); entered by several veins. Lemmas hairy (pilose), or hairless; when hairless glabrous; carinate (at least slightly so); without a germination flap; 5 nerved; with the nerves confluent towards the tip. Palea present; relatively long; entire (truncate), or apically notched (emarginate); awnless, without apical setae; not indurated (membranous); nerveless (rarely), or 1-nerved (rarely), or 2-nerved; 2-keeled, or keel-less. Lodicules present; free; membranous; ciliate; not toothed (usually entire); not or scarcely vascularized. Stamens 3. Anthers (2.5–)3.5–6 mm long; not penicillate; without an apically prolonged connective. Ovary apically hairy; with a conspicuous apical appendage, or without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; small to medium sized (3–5.5 mm long); longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small; not waisted. Endosperm hard; without lipid; containing only simple starch grains. Embryo with an epiblast, or without an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a short mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3–5 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower, more rectangular); differing markedly in wall thickness costally and intercostally (the costals with thicker, heavily pitted walls). Mid-intercostal long-cells mostly fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 46.5–51 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Small prickles abundant. Crown cells absent. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly solitary, a few pairs). Costal silica bodies predominantly horizontally-elongated crenate/sinuous (but varying in length, regularity and sinuosity so as to approach panicoid forms at the one extreme, the horizontal-smooth form at the other).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round topped). Midrib conspicuous (via a sharp keel and the large, heavily girdered bundle); with one bundle only. Bulliforms present in discrete, regular adaxial groups; exclusively in simple fans (in the furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the primaries, the rest with adaxial girders or strands only); forming figures (but at the most, only slight Is). Sclerenchyma all associated with vascular bundles.
Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly short-chain.
Cytology. Chromosome base number, x = 7. 2n = 14, 28, and 42. 2, 4, and 6 ploid. Haplomic genome content P.
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 15 species.
Distribution, phytogeography, ecology. Mediterranean to China and USSR.
Commonly adventive. Mesophytic, or xerophytic; species of open habitats. Steppe, etc., on dry stony soils.
Economic aspects. Significant weed species: A. cristatum. Cultivated fodder: A. cristatum.
Hybrids. Intergeneric hybrids with Hordeum (×Agrohordeum A. Camus), Leymus (×Leymopyron Tsvelev), Elytrigia (×Agrotrigia Tsvelev), Secale, Triticum (×Agrotrisecale Ciferri & Giacom., ×Agrotriticum Ciferri & Giacom.), Sitanion (×Agrositanion Bowden). See also ×Agroelymus A. Camus.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.
Special comments. Agropyron sensu stricto. Illustrations. • A. dasyanthum, as Triticum: Kunth (1835). • A. cristatum: Fl. Iraq, 1968
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: 12th March 2017. delta-intkey.com/grass’.