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The grass genera of the world

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

Malacurus Nevski

~ Leymus

Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous. Leaves auriculate. Leaf blades without cross venation. Ligule an unfringed membrane; truncate; 0.7–8 mm long.

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 (with sterile spikelets at the tip of the rachis).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the clusters reduced to pairs); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets paired; not secund.

Female-fertile spikelets. Spikelets 8–16 mm long; not noticeably compressed; disarticulating above the glumes; disarticulating between the florets (the rachilla very fragile). Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent.

Glumes two (much reduced); very unequal to more or less equal; joined (those of adjacent spikelets sometimes joined), or free; lateral to the rachis, or displaced (much reduced); hairless; glabrous; pointed; awned (awn-like); similar (subulate-setiform). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 2–4. Lemmas not becoming indurated; entire, or incised; awnless, or awned. Awns when present, 1; median; from a sinus, or apical; non-geniculate; much shorter than the body of the lemma (no more than 2 mm long); when present, deciduous. Lemmas hairy (densely lanate); non-carinate; without a germination flap; 7–9 nerved. Palea present; relatively long; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; not toothed; not or scarcely vascularized. Stamens 3. Ovary apically hairy. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; not grooved. Hilum long-linear. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs absent. Stomata common; 69–75 microns long. Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals (clearly sunken). Intercostal short-cells common; intercostal short-cells solitary and paired. Costal silica bodies absent to poorly developed (in the material seen); horizontally-elongated smooth, or rounded, or tall-and-narrow.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs. Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 42. 6 ploid.

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

Distribution, phytogeography, ecology. Central Asia.

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.


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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: 25th November 2016. delta-intkey.com’.

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