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The grass genera of the world

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

Elytrigia Desv.

~ Agropyron, Elymus

Including Trichopyrum (Nevski) Löve

Excluding Lophopyrum, Pascopyrum, Pseudoroegneria, Thinopyrum

Habit, vegetative morphology. Perennial; rhizomatous (or densely turf-forming). Culms 20–150 cm high; herbaceous; unbranched above. Culm internodes solid, or hollow. The shoots not aromatic. Leaves not basally aggregated; auriculate, or non-auriculate. Sheath margins joined (often, on vegetative shoots), or free. Leaf blades linear; apically flat; narrow; 1.2–10 mm wide; flat, or rolled (convolute); not pseudopetiolate; without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule an unfringed membrane; truncate; 0.2–1 mm long (tough membranous). Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile (sterile spikelets, when present, localised at the tip of the rachis). Plants outbreeding.

Inflorescence. Inflorescence a single spike (erect or drooping, linear). Rachides neither flattened nor hollowed, not winged. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; distichous; sessile to subsessile (the pedicels less than 0.3 mm long).

Female-fertile spikelets. Spikelets 7–23 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes, or falling with the glumes; not disarticulating between the florets, or disarticulating between the florets (the joints poorly developed). Rachilla prolonged beyond the uppermost female-fertile floret; hairy (rarely), or hairless (usually scabrous); the rachilla extension with incomplete florets. Hairy callus present, or absent. Callus short.

Glumes present; two; very unequal to more or less equal; shorter than the adjacent lemmas; free; lateral to the rachis; hairy (rarely), or hairless (glabrous); pointed, or not pointed; not subulate; awned, or awnless; non-carinate (or slightly so only towards the tip); similar (ovate, oblongate or lanceolate, not awnlike). Lower glume 3–11 nerved. Upper glume 3–11 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 3–7(–10). Lemmas similar in texture to the glumes (leathery, lanceolate); entire, or incised; pointed, or blunt; awnless, or mucronate, or awned. Awns when present, 1; from a sinus, or apical; non-geniculate; much shorter than the body of the lemma to much longer than the body of the lemma (to 20 mm long); entered by several veins. Lemmas hairy (somewhat pilose), or hairless; when hairless glabrous, or scabrous; non-carinate; without a germination flap; 5 nerved; with the nerves confluent towards the tip. Palea present; relatively long; 2-nerved; 2-keeled (the keels scabrous or ciliate). Lodicules present; 2; free; membranous; ciliate; usually not toothed; not or scarcely vascularized. Stamens 3. Anthers 5–8 mm long (relatively long). Ovary apically hairy. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit usually adhering to lemma and/or palea; medium sized (4–6 mm long); longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small. Endosperm hard; without lipid; containing only simple starch grains. Embryo with an epiblast (cf. Reeder’s illustration of E. repens); without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Seedling with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 2 veined, or 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 rectangular and fusiform; having markedly sinuous walls and having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries low dome-shaped, or parallel-sided (a few). Guard-cells overlapped by the interstomatals. Intercostal short-cells common; not paired (mostly solitary, a few pairs); silicified. Intercostal silica bodies tall-and-narrow, or saddle shaped, or cubical, or rounded. Crown cells present, or absent. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired (e.g. mainly solitary in E. repens). Costal silica bodies horizontally-elongated crenate/sinuous, or rounded (commonly), or saddle shaped (sometimes more or less cubical), or tall-and-narrow, or crescentic, or ‘panicoid-type’ (some in E. repens).

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

Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly short-chain.

Cytology. Chromosome base number, x = 7. 2n = 42, or 56, or 84 (rarely). 6, 8, and 12 ploid. Haplomic genome content E, J, and S, or S and X, or E and S (Trichopyrum). Haploid nuclear DNA content 4.3–5.9 pg (2 species).

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 8 species.

Distribution, phytogeography, ecology. North and south temperate.

Commonly adventive. Mesophytic, or xerophytic; halophytic, or glycophytic. Diverse habitats, including sand dunes.

Economic aspects. Significant weed species: E. repens (Quick Grass, Scutch, Couch).

Hybrids. Intergeneric hybrids with AgropyronAgrotrigia Tsvelev), HordeumElytrordeum Hylander, ×Elyhordeum Zizan & Petrowa), Aegilops, LeymusLeymotrigia Tsvelev), Lophopyrum, Secale, TriticumTrititrigia Tsvelev), Thinopyrum.

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: Metcalfe 1960; studied by us - E. pycnantha (Godron) A. Löve, E. repens (L.) Nevski.

Illustrations. • E. repens (as Triticum), general aspect: Eng. Bot. (1872). • cf. E. repens ssp. acutum (as Triticum acutum DC.), general aspect: Eng. Bot. (1872). • E. repens, general aspect, spikelets, flower. • cf. E. repens ssp. arenosa (as Triticum pungens), general aspect: Eng. Bot. (1872). • E. juncea (as Triticum junceum), general aspect: Eng. Bot. (1872). • Pollen antigens: Watson and Knox (1976)

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.’.