The grass genera of the world
Habit, vegetative morphology. Annual. Culms herbaceous. Leaves non-auriculate. Leaf blades without cross venation. Ligule an unfringed membrane; not truncate; 2–4 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 9–11 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; pointed (acuminate); awnless; carinate; similar. Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.
Female-fertile florets 2–4. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; all awned (including the lowest). Awns 1; median; dorsal; from well down the back (from the middle third); geniculate; entered by one vein. Lemmas hairy; non-carinate; without a germination flap; 5–6 nerved. Palea present; conspicuous but relatively short (about one half the lemma length); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea. Embryo small. Endosperm liquid in the mature fruit.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (seemingly involving only the midrib). Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally to differing markedly in wall thickness costally and intercostally (the walls of medium thickness, those of the costals tending to be thicker). Mid-intercostal long-cells rectangular (very long, rarely tending slightly to fusiform); having markedly sinuous walls (the sinuosity fairly fine and even, associated with conspicuous pitting). Microhairs absent. Stomata fairly common (but mostly confined to a single file on either side of the midrib); 45–54 microns long. Subsidiaries non-papillate; parallel-sided to dome-shaped. Guard-cells slightly but consistently overlapped by the interstomatals (the apparatus not noticeably sunken). Intercostal short-cells fairly common; in cork/silica-cell pairs (often), or not paired (a few solitary); silicified, or not silicified. Costal short-cells predominantly paired (both cells horizontally quite elongated). Costal silica bodies present and well developed; horizontally-elongated crenate/sinuous to horizontally-elongated smooth, or rounded (sometimes numerous, mostly more or less irregular), or crescentic (few).
Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous (by virtue of its large abaxial keel); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms not apparent in the poor material seen. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (only small adaxial strands, save for the small abaxial one with the midrib). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): cf. Pooideae (as a synonym?); Poodae; Poeae; Poinae. 1 species (P. blanchei).
Distribution, phytogeography, ecology. Asia Minor.
References, etc. Leaf anatomical: studied by us.
Illustrations. • P. blanchei, abaxial epidermis of leaf blade: 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: 11th December 2017. delta-intkey.com/grass’.