The grass genera of the world
Including Heteranthus Borkh., Heterochaeta Schult.
Excluding Gaudiniopsis, Pilgerochloa
Habit, vegetative morphology. Annual. Culms 10–70 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 1–2.5 mm wide; folded, or rolled (convolute); not pseudopetiolate; without cross venation; rolled in bud. Ligule an unfringed membrane; not truncate (acute, often lacerate); 2–4 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate, or a single raceme; open, or contracted; sometimes spicate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 8–15 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets (the lowermost floret persisting, falling later with the glumes and pedicel). Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus present. Callus short; pointed (in the upper florets).
Glumes two; very unequal; shorter than the adjacent lemmas; pointed (acute to acuminate); awnless; non-carinate; similar (herbaceous, with wide, scarious margins). Lower glume 3–7 nerved. Upper glume 3–9 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 2–7. Lemmas similar in texture to the glumes; not becoming indurated (papery, margins scarious); entire (the lowest), or incised (apically bidentate or bifid); awned (the L1 shorter and awnless but sometimes having an apical seta, the upper awned lemmas often bifid, with apical teeth or setae additional to the awn). Awns 1; median; dorsal; from well down the back; geniculate. Lemmas hairless; non-carinate; without a germination flap; 5 nerved. Palea present; relatively long; tightly clasped by the lemma; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 1.2–2.5 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit small (2.5 mm long); compressed laterally. Hilum short. Embryo small. Endosperm liquid in the mature fruit; with lipid.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common (fairly); 31–39 microns long. Subsidiaries tending to parallel-sided, or dome-shaped. Guard-cells overlapped by the interstomatals (mostly, slightly). Intercostal short-cells common; in cork/silica-cell pairs; silicified. Costal zones with short-cells. Costal short-cells predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous (fairly short), or rounded (a few), or crescentic (a few); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round topped). Midrib with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms seemingly not present in discrete, regular adaxial groups (bulliforms not apparent in material seen). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (the main bundles with an abaxial girder and an adaxial strand). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 5 species.
Distribution, phytogeography, ecology. Southern Europe.
Xerophytic; species of open habitats.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis.
References, etc. Leaf anatomical: this project.
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: 13th November 2017. delta-intkey.com/grass’.