Deschampsia P. Beauv.
After Dr. Deschamps of Saint-Omer.
Including Airidium Steud., Aristavena Albers & Butzin, Avenella Parl., Campella Link, Czerniaevia Ledeb., Erioblastus Honda, Homoiachne Pilger, Lerchenfeldia Schur, Podinapus Dulac
Excluding Periballia, Vahlodea
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent (but usually caespitose). Culms 8–200 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Sheath margins free. Leaf blades linear; narrow; 0.3–6 mm wide; setaceous, or not setaceous; flat, or folded, or rolled (convolute); without cross venation; persistent; rolled in bud, or once-folded in bud; ligule present; an unfringed membrane; not truncate; 3–15 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; outbreeding and inbreeding; exposed-cleistogamous, or chasmogamous. Viviparous (sometimes), or not viviparous.
Inflorescence. Inflorescence paniculate; usually open; with capillary branchlets, or without capillary branchlets. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 3–9 mm long (small, delicate); compressed laterally; disarticulating above the glumes; with distinctly elongated rachilla internodes between the florets (the lower floret sessile). Rachilla prolonged beyond the uppermost female-fertile floret (the terminal extension well developed); hairy (except D. chapmanii); the rachilla extension with incomplete florets, or naked (well developed beyond the uppermost floret). Hairy callus present. Callus short; blunt.
Glumes two; very unequal (rarely), or more or less equal; shorter than the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; pointed; awnless; carinate, or non-carinate; similar (subscarious to membranous, with thin margins). Lower glume 1 nerved, or 3 nerved. Upper glume 3 nerved, or 5 nerved. Spikelets with female-fertile florets only (usually), or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets when present, 1. Spikelets without proximal incomplete florets.
Female-fertile florets (1–)2(–3). Lemmas similar in texture to the glumes to decidedly firmer than the glumes (hyaline to cartilaginous); not becoming indurated; entire, or incised (2-lobed, 4-toothed or truncate); not deeply cleft; awned (usually), or awnless to mucronate (D. tenella and New Zealand relatives, distinguished from Poa by their denticulate lemma tip). Awns 1; median; dorsal; from well down the back (mostly from the base or lower half, a few from above the middle); slender, weakly geniculate, or non-geniculate; hairless (glabrous to scabridulous); much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairy (rarely), or hairless; non-carinate (rounded on the back); 4–7 nerved. Palea present; relatively long; tightly clasped by the lemma; awnless, without apical setae; not indurated (membranous); 2-nerved; 2-keeled. Lodicules present; 2; joined, or free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 0.3–2.5 mm long; not penicillate. Ovary glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved; compressed dorsiventrally, or not noticeably compressed. Hilum short. Pericarp thin (shining). Embryo large (rarely), or small; not waisted. Endosperm 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 narrow; 3 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 (fairly thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common, or absent or very rare; 36–39 microns long. Subsidiaries parallel-sided. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs, or not paired; when paired silicified. Costal short-cells predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded; sharp-pointed (rarely), or not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; traversed by columns of colourless mesophyll cells, or not traversed by colourless columns. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups; when clearly grouped, in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups (but sometimes forming an almost continuous layer); abaxial-hypodermal, the groups isolated (opposite the bulliforms), or abaxial-hypodermal, the groups continuous with colourless columns.
Phytochemistry. Leaves without flavonoid sulphates (3 species).
Special diagnostic feature. Lemmas without the characteristic Corynephorus awn. Female-fertile lemma not as in Lombardochloa (q.v.).
Cytology. Chromosome base number, x = 7 and 13. 2n = 14, 24, 26, 28, 32, 42, 52, and 56 (and 26+B). 2, 4, 6, and 8 ploid (and aneuploids: some complexes with n = 13, 14). Chromosomes ‘large’. Haploid nuclear DNA content 3.1–4.5 pg (3 species). Mean diploid 2c DNA value 10 pg (D. antarctica).
Taxonomy. Pooideae; Poodae; Aveneae.
Distribution, ecology, phytogeography. 40 species; North and South temperate, high altitude tropics. Commonly adventive. Helophytic, or mesophytic; shade species and species of open habitats. Meadows, upland grasslands and woods.
Holarctic, Paleotropical, Neotropical, Australian, and Antarctic. Boreal, Tethyan, and Madrean. African, Indomalesian, and Polynesian. Arctic and Subarctic, Euro-Siberian, Eastern Asian, Atlantic North American, and Rocky Mountains. Macaronesian, Mediterranean, and Irano-Turanian. Sudano-Angolan and West African Rainforest. Indo-Chinese and Papuan. Hawaiian. Caribbean, Pampas, and Andean. North and East Australian. New Zealand, Patagonian, and Antarctic and Subantarctic. European and Siberian. Canadian-Appalachian and Central Grasslands. Somalo-Ethiopian. Temperate and South-Eastern Australian. Antarctic.
Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia pygmaea, Puccinia praegracilis, Puccinia hordei, Puccinia recondita, and ‘Uromyces’ fragilipes. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Entyloma and Tilletia. Ustilaginaceae — Ustilago.
Economic importance. Significant weed species: D. caespitosa, D. flexuosa. Important native pasture species: D. flexuosa.
References, etc. Morphological/taxonomic: Koch 1979. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • General aspect, spikelet and floret details. • Abaxial epidermis of leaf blade. • Leaf blade transverse section
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
