The grass genera of the world
Type species: Type: P. thuarii P. Beauv.
Habit, vegetative morphology. Perennial; caespitose; geophytic, or not geophytic. Culms 25–200 cm high; woody and persistent, or herbaceous (from a woody or suffrutescent base); branched above, or unbranched above (often). The branching simple. Culm nodes glabrous. Culm internodes hollow. Plants unarmed. Young shoots intravaginal. Leaves mostly basal, or not basally aggregated; auriculate (P. thuarii), or non-auriculate (but hairy in the auricle positions). Leaf blades linear to linear-lanceolate; narrow (rigid or wiry, usually long and filiform, sometimes curled or squarrose); 1–4 mm wide; not pseudopetiolate; without cross venation; disarticulating from the sheaths, or persistent. Ligule a fringe of hairs; 1.5–2.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted to many spikeleted; paniculate; open, or contracted (sometimes scanty); with capillary branchlets, or without capillary branchlets; non-digitate (the branching sometimes trichotomous); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate (the pedicels usually long-capillary, expanded under the spikelets).
Female-fertile spikelets. Spikelets 13–25(–30) mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret (as a small extension). Hairy callus present. Callus short; blunt.
Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas (much exceeding them); hairy (puberulous, in P. dregeana), or hairless; other than in P. dregeana, glabrous; pointed (acute or acuminate); awned (setaceously acuminate), or awnless; carinate; similar (ovate-lanceolate, thin). Lower glume much exceeding the lowest lemma; 1 nerved, or 3 nerved. Upper glume 1 nerved, or 3 nerved. Spikelets occasionally with incomplete florets, or with female-fertile florets only (usually). The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 2. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated (membranous); incised; 2 lobed; deeply cleft; awned. Awns 3; median and lateral (the lateral lemma lobes each with a 1–7 mm bristle from the inner side, more or less adnate below); the median different in form from the laterals; from a sinus; geniculate (near the middle); hairless (scabrid); much longer than the body of the lemma; entered by several veins (3). The lateral awns shorter than the median (being loosely twisted or straight bristles, from the inner margins of the lobes). Lemmas hairy. The hairs not in tufts; not in transverse rows (in longitudinal rows between the veins). Lemmas non-carinate; having the margins lying flat on the palea; without a germination flap; 7 nerved, or 9 nerved (-11 nerved); with the nerves non-confluent. Palea present (hairy); relatively long; apically notched, or deeply bifid; awnless, without apical setae; textured like the lemma (membranous); 2-nerved; 2-keeled. Lodicules present; 2; joined (at the base), or free; fleshy; ciliate, or glabrous. Stamens 3. Anthers 4.5–5 mm long; not penicillate; without an apically prolonged connective. Ovary apically hairy (with a deciduous apical tomentum of branched hairs). Styles free to their bases (short). Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea (but enclosed by slightly hardened lemma and palea); small (3 mm long); ellipsoid, or subglobose. Hilum long-linear. Pericarp thick and hard (crustaceous); free. Embryo small.
Ovule, embryology. Micropyle oblique, or not noticeably oblique. Outer integument extensive, being absent only from the micropylar region, or covering no more than the chalazal half of the ovule; more than two cells thick at the micropylar margin. Inner integument continuous, the micropyle constricted; thickened around the micropyle, or not thickened around the micropyle. Synergids haustorial (weakly developed), or not haustorial; without large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking (or the costal long-cells narrower). Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (walls heavily thickened and pitted). Mid-intercostal long-cells rectangular, or rectangular to fusiform (in P. longiglumis); having markedly sinuous walls, or having straight or only gently undulating walls (in P. longiglumis). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies rounded. Costal short-cells predominantly paired. Costal silica bodies rounded, or tall-and-narrow (a few, in P. longiglumis); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade nodular in section; with the ribs very irregular in sizes. Midrib not readily distinguishable (except via its position); with one bundle only. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups (there being small, more or less distinct groups in the bases of the deep furrows); more or less in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (all the main bundles with Is or anchors). Sclerenchyma not all bundle-associated. The extra sclerenchyma in a continuous abaxial layer.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 5 species.
Distribution, phytogeography, ecology. South Africa.
Mesophytic; species of open habitats; glycophytic.
References, etc. Leaf anatomical: Ellis 1985.
Illustrations. • P. thuarii: P. Beauv. (1812). • P. thuarii: Kunth (1835), Dist. méthodique de la famille Graminées, t. 66. • Legend, Kunth (1835), Dist. méthodique de la famille Graminées, t. 66. • General aspect (P. macrocalycina): Gibbs Russell et al., 1990
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’.