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The grass genera of the world

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

Eremopyrum (Ledeb.) Jaub. & Spach

From the Greek eremos (desert) and puros (wheat), re habitat and resemblance of the inflorescence to that of wheat.

Habit, vegetative morphology. Annual; caespitose. Culms 20–40 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; auriculate. Sheath margins joined, or free. Leaf blades linear to linear-lanceolate; 1–7 mm wide; flat; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; truncate; 0.4–2 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence a single spike (the spikelets often divergent from the rachis); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes usually disarticulating; usually either falling entire, or disarticulating at the joints. Spikelets solitary; not secund; alternately distichous; sessile.

Female-fertile spikelets. Spikelets 9–25 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Callus blunt.

Glumes two; relatively large; more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; joined, or free; lateral to the rachis; pointed; not subulate; shortly awned, or awnless; carinate; similar (becoming very hard at maturity). Lower glume 1–4 nerved. Upper glume 1–4 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 3–6. Lemmas similar in texture to the glumes (leathery); not becoming indurated; awnless, or mucronate, or awned. Awns when present, 1; apical; non-geniculate; entered by several veins. Lemmas hairy, or hairless; carinate; 5–7 nerved; with the nerves confluent towards the tip. Palea present; conspicuous but relatively short; entire to apically notched; awnless, without apical setae, or with apical setae (via prolongation of the keels); thinner than the lemma (membranous); not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; toothed, or not toothed. Stamens 3. Anthers 0.5–1.3 mm long; not penicillate. Ovary apically hairy; with a conspicuous apical appendage (below the styles). Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit somewhat adhering to lemma and/or palea; small to large; longitudinally grooved; slightly compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular and fusiform; having straight or only gently undulating walls (these thin). Microhairs absent. Stomata common; 41.5–56 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare (excluding macrohair bases). Macrohair bases abundant. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (solitary). Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (the epidermis large-celled). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (strands only). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 14 and 28. 2 and 4 ploid. Haplomic genome content F. Haploid nuclear DNA content 5.5 pg (1 species, 2x). Mean diploid 2c DNA value 11 pg (1 species).

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 5 species.

Distribution, phytogeography, ecology. Mediterranean to central Asia.

Xerophytic; species of open habitats. Stony slopes, steppe, semi-desert.

Economic aspects. Important native pasture species: E. bonaepartis.

Rusts and smuts. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Ustilago.

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: studied by us - E. bonaepartis (Spreng.) Nevski E. distans (C. Koch) Nevski, E. orientale (L.) Jaub. & Spach, E. triticeum (Gaertn.) Nevski.

Illustrations. • E. distans: Fl. Iraq, 1968. • Spikelet of E. distans. • Inflorescence detail (E. triticeum). • Inflorescence detail (E. distans)

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.’.