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The grass genera of the world

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

Elymus L.

Elumos: old Greek name for a kind of grain.


Including Anthosachne Steud., Asperella Humb., Campeiostachys Drob., Clinelymus (Griseb.) Nevski, Goulardia Husn., Gymnostichum Schreb., Roegneria C. Koch, Semeiostachys Drob., Terellia Lunell, Zeia Lunell

Excluding Cockaynea (Elymus sect. Stenostachys), Elytrigia, Festucopsis, Hystrix, Lophopyrum, Leymus, Pascopyrum, Pseudoroegneria, Sitanion, Taeniatherum, Thinopyrum

Habit, vegetative morphology. Perennial; caespitose (or turf-forming). Culms 20–150(–200) cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots intravaginal. Leaves usually not basally aggregated; auriculate (the basal leaves), or non-auriculate (the stem leaves, sometimes). Sheath margins joined, or free. Leaf blades linear; apically flat; broad, or narrow; 1–18 mm wide; flat, or rolled (involute or convolute); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; truncate; 0.1–2 mm long. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants inbreeding; exposed-cleistogamous, or chasmogamous. Apomictic (in E. scaber (‘E. scabrus’) = ‘Agropyron scabrum’), or reproducing sexually.

Inflorescence. Inflorescence a single spike, or a false spike, with spikelets on contracted axes (erect or drooping); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent (i.e. with Hystrix and Sitanion excluded). Spikelets solitary, or paired, or in triplets (rarely up to four); not secund; distichous, or not two-ranked (sometimes not in regular rows, e.g. Clinelymus); sessile to subsessile (the pedicels 0.3 – 1.5 mm long); usually imbricate.

Female-fertile spikelets. Spikelets 8–25(–35) mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets, or disarticulating between the florets (usually, the joints well developed). Rachilla prolonged beyond the uppermost female-fertile floret; hairy (shortly pilose), or hairless (scabrous); the rachilla extension with incomplete florets. Hairy callus present (usually), or absent. Callus fairly long; blunt (obtuse-triangular).

Glumes two (well developed); relatively large; very unequal to more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; joined (basally), or free; when scoreable, lateral to the rachis; hairless; glabrous (or scabrid on the veins); without conspicuous tufts or rows of hairs; pointed (often), or not pointed (sometimes blunt); not subulate; awned (often, up to 8 mm long), or awnless; non-carinate (but the veins usually raised); similar (from lanceolate-ovate to narrow lanceolate). Lower glume 3–7 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets (2–)3–7(–9). Lemmas lanceolate-oblongate; less firm than the glumes to similar in texture to the glumes; not becoming indurated; entire; pointed; awnless, or mucronate, or awned. Awns when present, 1; median; apical; non-geniculate; straight, or recurving; much shorter than the body of the lemma to much longer than the body of the lemma (usually longer, up to 50 mm long, erect or more often divergent); entered by several veins. Lemmas hairy (shortly 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; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels usually scabrous, or hairy. Lodicules present; 2; free; membranous; usually ciliate; toothed, or not toothed (usually entire). Stamens 3. Anthers 1–4 mm long (rarely to 5 mm, nearly always ‘short’); not penicillate. Ovary apically hairy; with a conspicuous apical appendage (rarely, below the styles), or without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit usually adhering to lemma and/or palea; medium sized (5–9 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 without an epiblast; without a scutellar tail; with a negligible mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.

Seedling with a long mesocotyl; with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 3–5 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous, or lacking. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls, or having straight or only gently undulating walls (thin). Microhairs absent. Stomata absent or very rare (e.g. E. caninus), or common. Subsidiaries parallel-sided, or dome-shaped, or parallel-sided and dome-shaped. Intercostal short-cells common, or absent or very rare (e.g. E. interruptus); when present, in cork/silica-cell pairs, or not paired; silicified, or not silicified. Intercostal silica bodies when present, rounded (or oval), or crescentic, or tall-and-narrow. Crown cells present, or absent. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired (mostly solitary). Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded, or tall-and-narrow (usually), or crescentic, or saddle shaped (a tendency, in E. caninus).

Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with distinct, prominent adaxial ribs (low, rounded), or adaxially flat; when present, with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only, or having a conventional arc of bundles (e.g. E. interruptus). Bulliforms present in discrete, regular adaxial groups; in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma (e.g. E. caninus), or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. 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 = 28 and 42, or 56 (rarely). 4, 6, and 8 ploid (self pollinated). Haplomic genome content H and S, or S and Y (Roegneria). Chromosomes ‘large’. Nucleoli disappearing before metaphase.

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. About 150 species.

Distribution, phytogeography, ecology. Widespread extratropically in both hemispheres.

Commonly adventive. Mesophytic, or xerophytic.

Hybrids. Intergeneric hybrids with Sitanion, Triticum.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia striiformis.

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: Metcalfe 1960; studied by us - E. scabrus (R.Br.) Löve.

Illustrations. • E. scabrus, general aspect: Gardner, 1952. • Spikelet detail (E. scabrus). • Spikelet detail (E. scabrus). • Flower of E. scabrus. • cf. E. caninus (as Triticum caninum), general aspect: Eng. Bot. (1872)

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.’.