Leymus Hochst.
Including Aneurolepidium Nevski
Excluding Malacurus
Habit, vegetative morphology. Perennial; rhizomatous (or turf-forming). Culms 20–150 cm high; herbaceous; unbranched above. Culm internodes hollow. Young shoots extravaginal. Leaves mostly basal (often), or not basally aggregated; auriculate (the auricles lanceolate-crescentic), or non-auriculate. Sheath margins free. Leaf blades linear (harsh, glaucus, pungent); broad, or narrow; 2–15 mm wide; flat, or rolled (convolute); without cross venation; persistent; rolled in bud; an unfringed membrane; truncate, or not truncate; 0.2–1(–3) mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence a single spike, or a false spike, with spikelets on contracted axes (erect, linear, rarely oblongate); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets paired to in triplets (rarely solitary or in clusters of up to six); not secund; distichous; subsessile; usually imbricate.
Female-fertile spikelets. Spikelets (6–)8–20(–25) mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets (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, or absent. Callus blunt (triangular or rounded).
Glumes two; very unequal to more or less equal; shorter than the adjacent lemmas to long relative to the adjacent lemmas; joined (basally), or free; when scoreable, lateral to the rachis, or displaced (side by side); hairy (short pilose), or hairless (scabrous or rarely glabrous); when hairless glabrous (rarely), or scabrous; pointed (linear lanceolate to almost setiform); subulate, or not subulate; awned to awnless; carinate (often), or non-carinate; similar. Lower glume 1–3 nerved. Upper glume 1–3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets (2–)3–7(–12). Lemmas acute, with a cusp or awn; similar in texture to the glumes (leathery); not becoming indurated; entire; pointed; mucronate, or awned. Awns when present, 1; median; apical; non-geniculate; much shorter than the body of the lemma (up to 4 mm long); entered by several veins. Lemmas hairy (pilose), or hairless; when hairless glabrous, or scabrous; non-carinate; without a germination flap; 5 nerved, or 7 nerved; with the nerves confluent towards the tip. Palea present; relatively long (almost equalling the lemma); awnless, without apical setae; not indurated; 2-nerved; 2-keeled (pilose or scabrous along the keels, and often between them). Lodicules present; 2; free; membranous; ciliate; not toothed (usually entire). Stamens 3. Anthers 5–7 mm long (relatively long); not penicillate; without an apically prolonged connective. Ovary hairy; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; small to medium sized (2.5–9 mm long); longitudinally grooved; compressed dorsiventrally; usually 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.
First seedling leaf with a well-developed lamina. The lamina narrow.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous, or lacking. Papillae absent. Long-cells of similar wall thickness costally and intercostally, or differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells having markedly sinuous walls. Microhairs absent. Stomata common. Subsidiaries dome-shaped. Intercostal short-cells common; in cork/silica-cell pairs (and solitary); silicified. Costal short-cells predominantly paired (and solitary). Costal silica bodies rounded, or tall-and-narrow (or more or less rectangular); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (e.g., L. condensatus), or with the ribs very irregular in sizes (e.g. L. arenarius). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (in the furrows, often small and variable in size, cf. Ammophila); sometimes in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); forming ‘figures’, or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Plant and inflorescence not as in Lygeum (q.v.).
Cytology. Chromosome base number, x = 7. 2n = 28, 42, 56, and 84. 4, 6, 8, and 12 ploid. Haplomic genome content J and N. Chromosomes ‘large’.
Taxonomy. Pooideae; Triticodae; Triticeae.
Distribution, ecology, phytogeography. About 30 species; in the non-tropical southern hemisphere and especially mountains of central Asia and North America. Commonly adventive. Mesophytic, or xerophytic (often littoral or halophytic); species of open habitats; halophytic, or glycophytic. With a wide habitat range, including coastal sand dunes.
Holarctic. Boreal. Euro-Siberian, Atlantic North American, and Rocky Mountains. European and Siberian. Canadian-Appalachian.
Hybrids. Intergeneric hybrids with Agropyron (×Leymopyron Tsvelev), Elytrigia (×Leymotrigia Tsvelev), Psathyrostachys (×Leymostachys Tsvelev), Thinopyrum (several species involved). See also ×Elyleymus Baum.
Rusts and smuts. Rusts — Puccinia.
Economic importance. Including useful sandbinders.
References, etc. Morphological/taxonomic: Löve 1984; Atkins, Barkworth and Dewey 1984. Leaf anatomical: Metcalfe 1960 (after nomenclatural adjustments) and this project.
Illustrations. • Pollen antigens
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
