The grass genera of the world
Type species: Type: P. pannonicus (Host) Trin.
Habit, vegetative morphology. Annual; caespitose. Culms 5–40 cm high; herbaceous. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 1–3 mm wide; not setaceous; flat, or rolled (convolute). Ligule an unfringed membrane; not truncate; 3–4 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike (tough, cylindrical). Rachides hollowed. Spikelets all partially embedded in the rachis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; distichous; sessile.
Female-fertile spikelets. Spikelets 4–7 mm long; somewhat compressed laterally; falling with the glumes; not disarticulating between the florets. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas (exceeding them); lateral to the rachis; hairless; not pointed (obtuse, ovate); awnless; non-carinate; similar (leathery, strongly veined). Lower glume 5 nerved. Upper glume 5 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 2. Lemmas less firm than the glumes (membranous); not becoming indurated; entire; pointed; awnless; hairless; non-carinate; 0–2 nerved. Palea present; relatively long; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; not toothed. Stamens 3. Anthers 1.8–2.5 mm long. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea. Endosperm liquid in the mature fruit to hard; containing compound starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls (thin). Microhairs absent. Stomata common; (31.5–)36–39(–45) microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (solitary). Costal silica bodies horizontally-elongated crenate/sinuous; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms not apparent in the poor material seen. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (in the midrib only); forming figures (midrib only). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Plant and inflorescence not as in Lygeum (q.v.).
Cytology. Chromosome base number, x = 7 (?). 2n = 14 and 36. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 1 species.
Distribution, phytogeography, ecology. Southeast Europe.
Commonly adventive. Species of open habitats; halophytic, or glycophytic. In coastal sands and saline soils.
Rusts and smuts. Smuts from Tilletiaceae. Tilletiaceae Tilletia.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting. Illustrations. • P. pannonicus, as Rottboellia: Host (1801), Icones et descriptiones graminum austriacorum 1.
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’.