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The grass genera of the world

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

Pleuropogon R.Br.

From the Greek pleura (side) and pogon (beard), alluding to bristles at the base of the palea in the type species.

Including Lepitoma Steud., Lophochlaena Nees

Habit, vegetative morphology. Annual (rarely), or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–150 cm high; herbaceous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins joined. Leaf blades linear; narrow; 1–3 mm wide; usually flat; without cross venation; rolled in bud, or once-folded in bud. Ligule present; an unfringed membrane; not truncate; 2–6 mm long.

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

Inflorescence. Inflorescence a single raceme (rarely paniculate); open (rarely); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (the raceme unilateral); shortly pedicellate (often deflexed).

Female-fertile spikelets. Spikelets 8–15 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed; awnless; non-carinate; similar (membranous). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 6–20. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous to thinly leathery); not becoming indurated; entire to incised; when incised, not deeply cleft (bidentate, irregularly toothed or erose); mucronate to awned. Awns when present, 1; from a sinus, or apical; non-geniculate; much shorter than the body of the lemma; entered by one vein. Lemmas hairy, or hairless; 7 nerved. Palea present; awnless, without apical setae, or awned (from the base of the keels, and sometimes from higher on the keels as well); 2-nerved; 2-keeled. Palea keels winged (below). Lodicules present; 2; membranous. Stamens 3. Anthers 1.2–2 mm long. Ovary apically glabrous; without a conspicuous apical appendage. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; deep red. Pericarp fused. 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 present. Intercostal papillae over-arching the stomata; several per cell. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally to differing markedly in wall thickness costally and intercostally (the costals somewhat thicker). Mid-intercostal long-cells rectangular; having markedly sinuous walls (rarely), or having straight or only gently undulating walls. Microhairs absent. Stomata common; 36–39 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups, or in abaxial groups and in adaxial groups.

Cytology. Chromosome base number, x = 9, or 10. 2n = 40 and 42. 4 ploid. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Meliceae. 6 species.

Distribution, phytogeography, ecology. Western North America & circumpolar.

Helophytic; glycophytic.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - P. californicus (Nees) Benth., P. sabinii R. Br.

Special comments. Fruit data wanting. Illustrations. • P. californicus: Hitchcock and Chase (1950)

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: 11th December 2017.’.