The grass genera of the world
Type species: Type: P. monspeliensis (L.) Desf.
Including Chaetotropis Kunth, Nowodworskya Presl., Raspailia Presl., Santia Savi
Habit, vegetative morphology. Annual, or perennial; stoloniferous, or caespitose. Culms 2–120 cm high; herbaceous; branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins free. Leaf blades linear to linear-lanceolate; apically cucullate, or apically flat; narrow; 1–10 mm wide; setaceous (e.g., sometimes in P. tenellus), or not setaceous; flat (usually), or rolled (P. tenellus); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; truncate, or not truncate; 2–15 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (e.g., P. tenellus and P. monspeliensis at least sometimes exhibiting numerous small branches of abortive spikelets), or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile. Plants inbreeding; exposed-cleistogamous (presumably, in P. tenellus, P. griquensis), or chasmogamous.
Inflorescence. Inflorescence paniculate; bristly, contracted (usually, more ore or less), or open to contracted (e.g., P. viridis); more or less ovoid, or spicate, or more or less irregular. 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 1.5–3 mm long; somewhat compressed laterally; falling with the glumes (and the pedicel, or part of it, in most or all species). Rachilla terminated by a female-fertile floret. Hairy callus present (comprising the disarticulating part the base of the spikelet and the base of the glumes, in P. tenellus), or absent (usually). Callus short to long (represented by that part of the pedicel which falls with the spikelet).
Glumes present; two; relatively large; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; hairless (usually hispid or hispid and ciliolate), or hairy (P. tenellus, P. australis); usually scabrous; pointed (entire to bilobed); usually conspicuously awned (apically or from a notch), or awnless (e.g. P. viridis (semiverticillatus)); carinate to non-carinate; similar (chartaceous, usually scabrid, rarely hairy). Lower glume 1 nerved. Upper glume 1(–3) nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); smooth (shiny); not becoming indurated; entire to incised (truncate, finely toothed via excurrent nerves); not deeply cleft; awnless, or mucronate, or awned (usually). Awns when present (i.e. usually), 1, or 3; median (usually), or median and lateral (lateral nerves sometimes excurrent as short awns or mucros); from a sinus, or apical, or dorsal (conspicuously so only in P. tenellus and perhaps in P. australis); when dorsal, from near the top (usually subterminal), or from well down the back (from slightly above the middle in P. tenellus); non-geniculate (usually), or geniculate (P. tenellus and perhaps P. australis); hairless; much shorter than the body of the lemma to about as long as the body of the lemma (usually), or much longer than the body of the lemma (and much exceeding the glume awns, only in P. tenellus); entered by one vein; deciduous (usually), or persistent (P. tenellus). Awn bases twisted (P. tenellus), or not twisted; not flattened. Lemmas hairless; glabrous; non-carinate; without a germination flap; 5 nerved; with the nerves non-confluent. Palea present; relatively long, or conspicuous but relatively short (Chaetotropis, e.g. P. chilensis); tightly clasped by the lemma; entire (truncate), or apically notched; awnless, without apical setae, or with apical setae to awned (e.g., P. australis); thinner than the lemma to textured like the lemma; not indurated (hyaline); inconspicuously 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 2, or 3 (usually?), or 1 (in P. tenellus, P. griquensis). Anthers 0.2–0.6 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (usually), or free from both lemma and palea (e.g. P. viridis); small; fusiform (Chaetotropis), or ellipsoid; longitudinally grooved (usually), or not grooved (e.g. P. viridis); not noticeably compressed. Hilum short. Embryo large (rarely), or small; not waisted. Endosperm liquid in the mature fruit, or hard; with lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3–5 veined.
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, or fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; (31.5–)33–36(–37.5) microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare; when present, not paired (mostly solitary); not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous (mostly), or horizontally-elongated smooth (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, or nodular in section (rarely); with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent (rarely); nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings.
Phytochemistry. Leaves without flavonoid sulphates (1 species).
Cytology. Chromosome base number, x = 7. 2n = 14, 28, 42, 50, and 60 (not known for P. tenellus). 2, 4, 6, 7, and 8 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. 18 species.
Distribution, phytogeography, ecology. Mediterranean, southwest Asia.
Commonly adventive. Helophytic to mesophytic; species of open habitats; halophytic, or glycophytic. In moist ground.
Economic aspects. Significant weed species: P. monspeliensis, P. viridis.
Hybrids. Intergeneric hybrids with Agrostis (×Agropogon P. Fourn.).
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis and Puccinia coronata. Smuts from Tilletiaceae. Tilletiaceae Entyloma.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • P. monspeliensis, P. tenellus: Gardner, 1952. • P. chilensis, as Chaetotropis: Kunth (1835). • General aspect (P. viridis): Gibbs Russell et al., 1990. • General aspect (P. monspeliensis): Gibbs Russell et al., 1990. • P. monspeliensis, general aspect: Eng. Bot. (1872). • xAgropogon littoralis (Agrostis stolonifera x P. monspeliensis, as P. littoralis): 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’.