The grass genera of the world
Type species: Type: P. distans (L.) Parl., type cons..
Including Atropis (Trin.) Griseb., Pseudosclerochloa
Habit, vegetative morphology. Annual (a few), or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 4–100 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal, or intravaginal. Leaves not basally aggregated; non-auriculate. Sheath margins generally free (rarely closed basally to almost one third their length). Leaf blades linear; apically cucullate; narrow; 0.5–5 mm wide; setaceous, or not setaceous; flat, or folded, or rolled; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; truncate, or not truncate; 0.5–4.5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding and inbreeding; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence paniculate (rarely reduced and racemelike); open (usually), or contracted. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 2–13 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus absent (but the lemma base often hairy).
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed (oblong); awnless; non-carinate; similar. Lower glume 1(–2) 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 2–10. Lemmas similar in texture to the glumes (membranous, thinner apically); not becoming indurated; entire (or erose, often ciliolate); pointed, or blunt; awnless; hairy (often only at the base), or hairless; non-carinate (or rarely carinate); having the margins lying flat on the palea; 5 nerved. Palea present; relatively long; apically notched (emarginate); awnless, without apical setae; 2-nerved; 2-keeled. Palea keels scabrous (or scaberulous), or hairy. Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 0.3–2.5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved, or not grooved; compressed dorsiventrally. Hilum short (round to oval). Embryo small; not waisted. Endosperm hard; without lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting, or overlapping.
Seedling with a loose coleoptile, or with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 1–3 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell. Long-cells similar in shape costally and intercostally (but the costals tending to be fusiform); of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common; in P. stricta 24–27 microns long. Subsidiaries parallel-sided, or dome-shaped (slightly). Guard-cells overlapped by the interstomatals (in some species the stomata are sunken, with access to the exterior only via a triangular pore). Intercostal short-cells common; in cork/silica-cell pairs, or not paired (some solitary, some triplets); silicified, or not silicified. Intercostal silica bodies rounded (elliptical), or crescentic. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded (predominating), or crescentic; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Midrib with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (sometimes of small cells, irregular in size, at the bases of furrows - cf. Ammophila); when regularly grouped, in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings.
Cytology. Chromosome base number, x = 7. 2n = 14, 28, 35, 42, 49, 56, 70, and 77. 2–11 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Coleanthinae. About 80 species.
Distribution, phytogeography, ecology. North temperate.
Commonly adventive. Helophytic, or mesophytic; usually halophytic.
Economic aspects. Cultivated fodder: P. airoides. Important native pasture species: P. airoides.
Hybrids. Intergeneric hybrids with Phippsia - ×Pucciphippsia Tsvelev.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, and Uromyces dactylidis. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Entyloma and Urocystis. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • P. stricta (as Glyceria): Hooker, Fl. Tasmaniae (1860). • Inflorescence and spikelet of P. stricta: this project. • P. stricta, abaxial epidermis of leaf blade: this project. • cf. P. distans (as Sclerochloa eu-distans), general aspect: Eng. Bot. (1872). • cf. P. fasciculata (as Sclerochloa borreri), general aspect: Eng. Bot. (1872). • cf. P. maritima (as Sclerochloa), general aspect: Eng. Bot. (1872). • P. rupestris (as Sclerochloa procumbens), general aspect: Eng. Bot. (1872)
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’.