The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 40–200 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; auriculate (from the base of the blade). Leaf blades linear to linear-lanceolate; broad; 6–15 mm wide (to 15 mm wide); flat, or rolled; not pseudopetiolate; cross veined; persistent; rolled in bud. Ligule an unfringed membrane (with lacerate margins); not truncate; 3–8.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence paniculate; open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 8–10 mm long; not noticeably compressed; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret (even when there is only one floret); hairless (minutely scabrid). Hairy callus present, or absent. Callus short; blunt.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; glabrous; pointed (acute or acuminate); awnless; more or less carinate; similar. Lower glume shorter than the lowest lemma; 1–3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; when present, awned. Spikelets without proximal incomplete florets.
Female-fertile florets 1–2. Lemmas similar in texture to the glumes; not becoming indurated; incised; not deeply cleft (only notched); awned. Awns 1; median; dorsal, or apical; when apical, from near the top; non-geniculate, or geniculate; hairless (scabrid); much longer than the body of the lemma; entered by one vein. Lemmas hairy (with a tuft above the callus), or hairless; non-carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; entire; awnless, without apical setae (glabrous); textured like the lemma; not indurated (membranous); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 3 mm long; not penicillate; without an apically prolonged connective. Ovary apically hairy. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit medium sized (6–7 mm long); longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small. 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.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (costals longer and narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 40.5–42–45 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals (sunken). Intercostal short-cells absent or very rare (prickles only). Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade nodular in section; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups (between the bundles); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 28.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Loliinae (?). 3 species.
Distribution, phytogeography, ecology. East tropical and South Africa, Madagascar.
Mesophytic; shade species; glycophytic. In forests.
Economic aspects. Important native pasture species: P. engleri, P. silvaticus.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • P. africana (as P. silvaticus): Jacques-Félix, 1962
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’.