The grass genera of the world
Habit, vegetative morphology. Annual. Culms herbaceous. Leaves auriculate, or non-auriculate. Leaf blades linear; narrow; 1.5–6 mm wide; usually flat; without cross venation. Ligule an unfringed membrane; truncate; 0.5 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 (rarely, sterile at the extremities of the inflorescence).
Inflorescence. Inflorescence a single spike (glabrous, linear, usually very long). Rachides hollowed. Spikelets all partially embedded in the rachis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes with substantial rachides; disarticulating; disarticulating at the joints. Spikelets solitary; not secund; distichous.
Female-fertile spikelets. Spikelets 8–15 mm long; compressed laterally; falling with the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Callus very short; blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; lateral to the rachis; not pointed; not subulate; awnless; non-carinate; similar (trapezoid or rectangular). Lower glume 3–9 nerved. Upper glume 4–9 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 4–8. Lemmas less firm than the glumes; not becoming indurated; entire; blunt; awnless; hairy, or hairless; non-carinate; without a germination flap; 5 nerved; with the nerves non-confluent. Palea present; relatively long; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 3.5–4.8 mm long. Ovary apically hairy; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; small to medium sized (3.5–4 mm long); ellipsoid; shallowly longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo large to small (to about 1/3 the caryposis length); with an epiblast.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally, or markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally, or differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells rectangular (mostly); having straight or only gently undulating walls. Microhairs absent. Stomata common; 39–41 microns long. Subsidiaries parallel-sided and dome-shaped. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare (a few, solitary, not silicified, near veins). Crown cells present. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous (predominantly), or horizontally-elongated smooth (few).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. 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 = 14. 2 ploid. Haplomic genome content Z.
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Triticinae. 1 species (A. muticum).
Distribution, phytogeography, ecology. W. Asia.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: studied by us.
Illustrations. • A. muticum: Fl. Iraq, 1968. • A. muticum, abaxial epidermis of leaf blade: this project. • A. muticum, abaxial epidermis of leaf blade with ‘crown cells’: this project. Amblyopyrum muticum. Showing ‘crown cells’.
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. delta-intkey.com/grass’.