The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Brachypodium P. Beauv.

From the Greek brachys (short) and podion (a little foot), in reference to subsessile spikelets.

Type species: Type: B. pinnatum P.Beauv.

Including Brevipodium A. & D. Löve, Trachynia Link, Tragus Panzer

Habit, vegetative morphology. Annual, or perennial; rhizomatous to caespitose. Culms 2–200 cm high; herbaceous; branched above, or unbranched above. Culm nodes hairy. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins free. Leaf blades linear; apically flat; broad (rarely), or narrow; 3–12 mm wide; flat, or rolled (convolute); not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; truncate, or not truncate; 1–6 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; inbreeding.

Inflorescence. Inflorescence few spikeleted; a single raceme, or paniculate (rarely); open. Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (drooping to one side), or not secund; distichous; pedicellate.

Female-fertile spikelets. Spikelets 13–40 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis; pointed; awned, or awnless; non-carinate; similar (lanceolate). Lower glume 5–7 nerved. Upper glume 7–9 nerved, or 11 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awned, or awnless.

Female-fertile florets 8–22. Lemmas ovate-lanceolate to acuminate; similar in texture to the glumes; not becoming indurated; entire; pointed; awned. Awns 1; median; apical; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma; entered by several veins (3–5). Lemmas hairless; non-carinate; (5–)7–9 nerved. Palea present; relatively long; entire (truncate); awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; not toothed. Stamens 3. Anthers 0.4–4.5 mm long; not penicillate. Ovary apically hairy; with a conspicuous apical appendage (below the styles), 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 (Trachynia), or free from both lemma and palea; medium sized; 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 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; 7–9 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 (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (rarely), or having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare, or common; in B. distachyon 24–27 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; not paired (mainly solitary); silicified (often, and with adjacent prickles), or not silicified. Intercostal silica bodies when present, rounded, or tall-and-narrow. Crown cells present, or absent. Costal short-cells conspicuously in long rows, or predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, rounded, and tall-and-narrow.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (or the groups of fairly uniform cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in three or more rings.

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 5, 7, 9, and 10. 2n = 10, 14, 16, 18, 28, 30, 42, and 56. 2, 4, 6, and 8 ploid (and aneuploids). Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Brachypodieae. Soreng et al. (2015): Pooideae; Brachypodieae. 16 species.

Distribution, phytogeography, ecology. Temperate, and tropical mountains.

Commonly adventive. Mesophytic; shade species and species of open habitats.

Economic aspects. Significant weed species: B. distachyon (= Trachynia).

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, Puccinia brachypodii-phoenicoidis, and Puccinia recondita. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - B. distachyon (L.) Beauv., B. pinnatum (L.) Beauv.

Illustrations. • B. sylvaticum, general aspect: Eng. Bot. (1872). • B. pinnatum, general aspect: Eng. Bot. (1872). • B. flexum: Gibbs Russell et al., 1990. • Inflorescence, spikelet and floret (B. distachyon)

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.’.