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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; this project.

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)


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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: 13th November 2017. delta-intkey.com/grass’.

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