The grass genera of the world
From the Greek brizo (to be sleepy or nodding), referring to nodding spikelets.
Including Brizochloa Jir sek & Chrtek (= Briza humilis), Chascolytrum Desv., Chondrachyrum Nees, Macrobriza (Tsvel.) Tsvel., Tremularia Fabric.
Excluding Calosteca, Lombardochloa
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or caespitose. Culms 5–100 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal, or intravaginal. Leaves not basally aggregated; non-auriculate. Sheath margins free. Leaf blades linear to linear-lanceolate; narrow; 1–10 mm wide; flat; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; not truncate; 0.8–2.5 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; outbreeding and inbreeding; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets (the spikelets drooping elegantly - quaking grass). Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; secund (drooping to one side), or not secund; pedicellate.
Female-fertile spikelets. Spikelets 2.5–25 mm long; compressed laterally; disarticulating above the glumes; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent. Callus short.
Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; not pointed; awnless; carinate, or non-carinate; similar (broad and cordate, thin and papery). Lower glume 3–15 nerved. Upper glume 3–15 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless.
Female-fertile florets 4–20. Lemmas as broad as long, gibbous and umbonate, cordate; similar in texture to the glumes; not becoming indurated; entire, or incised (obtuse, cuspidate, bidentate or mucronate); awnless, or mucronate (the mucro less than 1.5 mm long); hairy, or hairless; non-carinate; without a germination flap; 7–15 nerved. Palea present; conspicuous but relatively short; awnless, without apical setae (and with no apical appendage, by contrast with Calosteca); not indurated (hyaline); 2-nerved; 2-keeled. Lodicules present; 2; joined, or free; membranous; glabrous; toothed (rarely), or not toothed; not or scarcely vascularized. Stamens 3. Anthers 0.4–2.4 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea, or free from both lemma and palea; small; compressed dorsiventrally. Hilum short, or long-linear. Embryo small; not waisted. Endosperm liquid in the mature fruit (rarely), 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; 3–5 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform (contrasting with the smaller, narrower costals); having markedly sinuous walls (thin), or having straight or only gently undulating walls. Microhairs absent. Stomata common (usually), or absent or very rare. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common (e.g., B. triloba), or absent or very rare; when present, in cork/silica-cell pairs. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded, or tall-and-narrow (or tending to rectangular).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade nodular in section, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures, or nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Tissues of the culm bases with little or no starch. Leaves without flavonoid sulphates (several species).
Special diagnostic feature. Lemmas as broad as long, gibbous and umbonate, cordate at base.
Cytology. Chromosome base number, x = 5 and 7. 2n = 10, 14, and 28. 2 and 4 ploid (and aneuploid). Chromosomes large. Haploid nuclear DNA content 5.2–10.8 pg (6 species, mean 7.3). Mean diploid 2c DNA value 17.7 pg (3 species, 14.6–21.6).
Taxonomy. Pooideae; Poodae; Poeae.
Distribution, ecology, phytogeography. 16 species; North temperate, South America. Commonly adventive. Mesophytic; mostly species of open habitats. On dry to moist soils.
Holarctic, Paleotropical, Neotropical, and Antarctic. Boreal, Tethyan, and Madrean. African and Indomalesian. Euro-Siberian and Atlantic North American. Macaronesian, Mediterranean, and Irano-Turanian. Saharo-Sindian. Indian and Papuan. Caribbean, Central Brazilian, Pampas, and Andean. Patagonian. European. Southern Atlantic North American and Central Grasslands.
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.
Economic importance. Significant weed species: B. maxima, B. media, B. minor. Cultivated ornamentals - especially B. maxima.
References, etc. Morphological/taxonomic: Mattei 1975, Rosengurtt and Arrillaga 1979, Nicora and Rúgolo de Agrasar 1981. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • General aspect (B. maxima, B. minor). • General aspect. • Inflorescence detail (B. subaristata). • Spikelets (B. subaristata). • Floret of B. maxima. Briza maxima. Small palea within broad, cordate lemma. • Caryopsis of B. maxima. Briza maxima. With remnants of adherent palea, and a long-linear hilum. • Caryopsis details of B. maxima. Briza maxima. ‘Small’ embryo, and remains of adherent palea margins. • Germination in B. maxima. Briza maxima. Radicle emerging through split lemma.
The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using 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, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG).
Cite this publication as: ‘Watson, L., 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: 2nd April 2015. delta-intkey.com’.