The grass genera of the world
Type species: Type: D. glomerata L.
Including Amaxitis Adans., Trachypoa Bub.
Habit, vegetative morphology. Perennial; densely caespitose (with short, oblique rhizomes and/or stolons). Culms 15–200 cm high; herbaceous; unbranched above; tuberous, or not tuberous; 3–7 noded. Culm nodes exposed, or hidden by leaf sheaths; glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins joined (to halfway, at least in the upper leaves). Sheaths keeled, terete. Leaf blades linear to linear-lanceolate; broad, or narrow; 2–14 mm wide; flat, or folded, or rolled (involute); without cross venation; persistent; once-folded in bud. Ligule an unfringed membrane; not truncate; 2–17 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (usually), or of sexually distinct forms on the same plant (sometimes with rudimentary spikelets at the base of the inflorescence or at the bases of spikelet clusters). Plants outbreeding.
Inflorescence. Inflorescence paniculate; open, or contracted. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets secund (in dense, one-sided clusters terminating the panicle branches); subsessile, or pedicellate (shortly so).
Female-fertile spikelets. Spikelets 4–8(–9.4) mm long; elliptic, or ovate; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent. Callus short; blunt.
Glumes two; relatively large; very unequal to more or less equal; shorter than the spikelets to about equalling the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas (from about half to more than 3/4 as long); pointed; awned to awnless; carinate; similar (membranous, somewhat curved, often asymmetric about the midvein). Lower glume 1–3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped (rudimentary).
Female-fertile florets 2–5. Lemmas decidedly firmer than the glumes (papery); not becoming indurated; entire; pointed; awned. Awns 1; median; dorsal, or apical; from near the top; non-geniculate; much shorter than the body of the lemma; entered by one vein, or entered by several veins. Lemmas hairy, or hairless; scabrous (or scabrous and pilose); carinate; 5 nerved. Palea present; relatively long; tightly clasped by the lemma; apically notched; thinner than the lemma (membranous); 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 1.5–4.5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (to the palea), or free from both lemma and palea; small; oblong to ellipsoid; not grooved; compressed dorsiventrally to not noticeably compressed. Hilum short. Embryo small; not waisted. Endosperm liquid in the mature fruit, or hard; with lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a long mesocotyl; with a tight coleoptile. 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 similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform (slightly); having markedly sinuous walls, or having straight or only gently undulating walls (rarely). Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare; not paired; not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth (a few).
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. Midrib conspicuous (with a median bulliform group in its adaxial groove); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (apart from a large group above the median vascular bundle). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly long-chain. Leaves without flavonoid sulphates (1 species).
Cytology. Chromosome base number, x = 7. 2n = 14 and 28 (+ 0–4 B). 2 and 4 ploid (+0–4B). Chromosomes large. Haploid nuclear DNA content 4.9 pg (1 species, 2x). Mean diploid 2c DNA value 9.8 pg (1 species).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Dactylidinae. 1 species (or up to 5, by recognition of minor segregates).
Distribution, phytogeography, ecology. Temperate Eurasia.
Commonly adventive. Mesophytic; shade species and species of open habitats. Meadows, woodlands and disturbed ground, in moist to dry places.
Economic aspects. Significant weed species: D. glomerata. Cultivated fodder: D. glomerata (Orchard Grass).
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, Puccinia recondita, and Uromyces dactylidis. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Entyloma, Tilletia, and Urocystis. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: this project.
Illustrations. • D. glomerata, general aspect: Eng. Bot. (1872). • General aspect and spikelet (D. glomerata). • Ligule (D. glomerata). • Inflorescence detail (D. glomerata). • Inflorescence detail. Dactylis glomerata. Four spikelets. • Spikelet of D. glomerata
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’.