| # The grass genera of the world |

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

### Hordelymus (Jessen) C.O. Harz

Including Cuviera Koel.

Habit, vegetative morphology. Perennial; caespitose (from short, creeping rhizomes). Culms 40–110 cm high; herbaceous. Culm nodes hairy. Leaves auriculate. Leaf blades linear; broad, or narrow; 4–14 mm wide; flat; without cross venation. Ligule an unfringed membrane; truncate; 0.7–1 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile (the central spikelet of each triplet imperfect).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the spikelets in triplets on reduced axes, like Hordeum but all pedicellate); contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent (the rachis tough). Spikelets in triplets; not secund; distichous; consistently in ‘long-and-short’ combinations; unequally pedicellate in each combination. The ‘shorter’ spikelets (i.e. the central member of each triplet) male-only, or sterile. The ‘longer’ spikelets (i.e. the lateral members) hermaphrodite.

Female-fertile spikelets. Spikelets about 12 mm long; compressed dorsiventrally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension usually with incomplete florets (the upper of the two florets usually being imperfect, and with bristle beyond it).

Glumes two; more or less equal; long relative to the adjacent lemmas; joined; displaced (side by side); hairless; scabrous; subulate to not subulate (linear subulate to linear); awned (but not awnlike); carinate, or non-carinate; similar. Lower glume 3 nerved. Upper glume 3 nerved. Spikelets usually with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 1(–2) (the upper floret occasionally being also perfect). Lemmas lanceolate acuminate to the awn; similar in texture to the glumes; entire; pointed; awned. Awns 1; median; apical; non-geniculate; hairless; about as long as the body of the lemma to much longer than the body of the lemma; entered by several veins. Lemmas hairless; scabrous; non-carinate; without a germination flap; 5–7 nerved. Palea present (narrow); relatively long; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; not toothed; not or scarcely vascularized. Stamens 3. Anthers 3–4 mm long. Ovary apically hairy; below the styles. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit slightly adhering to lemma and/or palea; medium sized (7–8 mm long); longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells differing markedly in wall thickness costally and intercostally (costals thicker-walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Subsidiaries low dome-shaped, or parallel-sided. Intercostal short-cells absent or very rare. Small prickles numerous. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (the few seen mostly solitary). Costal silica bodies (the feww seen) horizontally-elongated crenate/sinuous, or horizontally-elongated smooth.

Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with the ribs very irregular in sizes. Midrib conspicuous (the girders more massive). Bulliforms present in discrete, regular adaxial groups; in simple fans. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 28 and 70. 4 and 10 ploid. Haplomic genome content H and T. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 1 species (H. europaeus).

Distribution, phytogeography, ecology. Europe, Western Asia.

Shade species. Woodland.

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

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: Metcalfe 1960, and studied by us.

Illustrations. • Hordelymus europaeus (as Hordeum sylvaticum), 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: 15th June 2025. delta-intkey.com’.

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