The grass genera of the world
Habit, vegetative morphology. Annual. Culms herbaceous. Leaves auriculate, or non-auriculate. Leaf blades linear; narrow; 1–3 mm wide; flat, or rolled (convolute); without cross venation. Ligule an unfringed membrane; unevenly truncate; 0.2–0.5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a single spike (with embedded spikelets). Rachides hollowed. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating; disarticulating at the joints. Spikelets solitary; not secund; distichous.
Female-fertile spikelets. Spikelets 7–10 mm long; not noticeably compressed; falling with the glumes. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; displaced (side by side, both abaxial); without conspicuous tufts or rows of hairs; pointed, or not pointed (acute to obtuse); not subulate; awnless; non-carinate; similar (asymmetrical). Lower glume 3–7 nerved. Upper glume 5–9 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 1–2. Lemmas acute; less firm than the glumes (very soft); not becoming indurated; entire; pointed; awnless; hairy; non-carinate; without a germination flap; 3–5 nerved. 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 0.5–2.2 mm long. Ovary apically hairy. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (slightly); medium sized (4–6.2 mm long); shallowly longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo large to small (up to 1/3 the length of the caryopsis). Endosperm containing only simple starch grains. Embryo with an epiblast.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; differing markedly in wall thickness costally and intercostally (costals with thicker walls). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common; 60–63 microns long. Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals (mostly, slightly). Intercostal short-cells absent or very rare. Prickle/macrohair bases abundant. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly solitary). Costal silica bodies horizontally-elongated crenate/sinuous (some almost qualifying as nodular), or rounded (a few).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. 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 the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (large bundles only); forming figures. Sclerenchyma all associated with vascular bundles (except for massive groups in the blade margins).
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Haplomic genome content O. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 2 species.
Distribution, phytogeography, ecology. Southwest & Central Asia.
Species of open habitats. Dry slopes.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.
Illustrations. • H. persica: Fl. Iraq, 1968
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: 14th June 2017. delta-intkey.com/grass’.