| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Pentapogon R.Br.

From the Greek pente (five) and pogon (beard), referring to five-awned lemmas.

Type species: Type: P. billardierei R.Br., nom. illeg..

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 20–60 cm high; herbaceous. Culm nodes hairy. Culm internodes hollow. Leaves auriculate, or non-auriculate. Leaf blades apically cucullate; narrow; not setaceous (inrolled); not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; truncate, or not truncate; 0.5–2 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; open (the branches scabrid). 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 5–15 mm long; compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present.

Glumes two; very unequal to more or less equal; (the longer) exceeding the spikelets; (the longer) long relative to the adjacent lemmas (exceeding them); hairless (scabrid, especially on the keels); pointed; shortly awned, or awnless; carinate; similar (membranous, acuminate). Lower glume 1(–3) nerved. Upper glume 3(–5) nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (leathery); becoming indurated to not becoming indurated; incised; 4 lobed; deeply cleft (deeply incised into 4 lanceolate, awn-tipped lobes, with a long median awn); awned. Awns 5; median and lateral; the median different in form from the laterals; dorsal; from near the top (i.e., arising just behind the sinus); geniculate; hairless (scabrid); much longer than the body of the lemma; entered by one vein. The lateral awns shorter than the median (straight, slender). Lemmas hairless; glabrous; non-carinate; 5 nerved. Palea present; relatively long, or conspicuous but relatively short, or very reduced; tightly clasped by the lemma; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small; not noticeably compressed. Hilum short. Embryo small. Endosperm liquid in the mature fruit (Clayton and Renvoize 1986).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (but the costals nuch smaller); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular to fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous and horizontally-elongated smooth, or rounded (a few); 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 more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. 1 species (P. quadrifidus).

Distribution, phytogeography, ecology. Australia, Tasmania.

Mesophytic, or xerophytic; glycophytic. Open woodland.

References, etc. Leaf anatomical: Metcalfe 1960, and studied by us.

Illustrations. • Pentapogon quadrifidus, as P. billardieri: Turner, Austr. Grasses (1895). • Inflorescence detail (Pentapogon quadrifidus). • Spikelet of Pentapogon quadrifidus. • Spikelet base (Pentapogon quadrifidus).

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: 15th June 2025. delta-intkey.com’.

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