The grass genera of the world
Type species: Type: A. pratensis L.
Including Alopecuropsis Opiz, Colobachne P. Beauv., Tozzettia Savi
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–110 cm high; herbaceous; branched above, or unbranched above; tuberous (e.g. A. bulbosus), or not tuberous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; apically cucullate; narrow; 0.7–10(–12) mm wide; flat, or rolled; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; truncate, or not truncate; 1–6 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants outbreeding.
Inflorescence. Inflorescence paniculate; contracted; capitate, or more or less ovoid, or spicate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 2–7 mm long; compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas; joined (below), or free; pointed; awnless; carinate (the keels ciliate); similar (membranous). Lower glume 1–3 nerved. Upper glume 2 nerved, or 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas often with the margins connate below; less firm than the glumes to similar in texture to the glumes (hyaline); not becoming indurated; entire; pointed, or blunt; awned. Awns 1; median; dorsal; from well down the back; geniculate; much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairy, or hairless; non-carinate; 5 nerved, or 7 nerved. Palea present (rarely), or absent (usually); when present, very reduced; awnless, without apical setae; not indurated. Lodicules absent. Stamens 3. Anthers 0.3–3.5 mm long; not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small. 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 loose coleoptile, or with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina broad, or narrow; erect; 3 veined.
Abaxial leaf blade epidermis. Papillae present, or absent. Mid-intercostal long-cells having markedly sinuous walls (rarely), or having straight or only gently undulating walls. Microhairs absent. Stomata common; 33–37.5 microns long (in A. pratensis). Subsidiaries parallel-sided. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous to horizontally-elongated smooth.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (or the cells fairly uniform in size within the groups). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent; nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings, or in three or more rings.
Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly long-chain. Leaves containing flavonoid sulphates (1 species).
Special diagnostic feature. Spikelets not borne as in Cornucopiae (q.v.).
Cytology. Chromosome base number, x = 7. 2n = 14, 28, 42, 56, and 100. 2, 4, 6, 8, 14, and 17 ploid. Chromosomes large. Haploid nuclear DNA content 3 pg (1 species).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 36 species.
Distribution, phytogeography, ecology. Eurasia & temperate South America.
Commonly adventive. Helophytic, or mesophytic; species of open habitats; halophytic (A. bulbosus), or glycophytic. Damp meadows to stony slopes.
Economic aspects. Significant weed species: A. aequalis, A. geniculatus, A. myosuroides (Black Twitch, in temperate cereal crops). Cultivated fodder: A. pratensis. Important native pasture species: A. pratensis.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, Puccinia brachypodii, Puccinia recondita, and Uromyces dactylidis. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Entyloma, Tilletia, and Urocystis. Ustilaginaceae Sphacelotheca and Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • A. bulbosus, A. myosuroides: John Curtis, 1834. • A. bulbosus, general aspect: Eng. Bot. (1872). • A. borealis (as A. alpinus): general aspect, Eng. Bot. (1872). • A. geniculatus, A. myosuroides, A. pratensis: Gardner, 1952. • A. myosuroides (as A. agrestis), general aspect: Eng. Bot. (1872). • A. magellanicus: Hooker, Fl. Antarctica (1844). • A. fulvus, general aspect: Eng. Bot. (1872). • A. pratensis, general aspect: Eng. Bot. (1872)
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’.