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The grass genera of the world

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

Pappophorum Schreber

From the Greek pappos (pappus) and phoros (bearing), alluding to lemmas with a pappus-like crown.

Including Polyraphis (Trin.) Lindley

Habit, vegetative morphology. Perennial; caespitose. Culms 30–150(–200) cm high; herbaceous. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear (glabrous); narrow; 2–6 mm wide; flat, or rolled (rigid); exhibiting multicellular glands abaxially (at the base of macrohairs). The abaxial leaf blade glands intercostal. Leaf blades not pseudopetiolate; without cross venation. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes when present, in the leaf sheaths (sometimes basal and highly modified).

Inflorescence. Inflorescence paniculate; open, or contracted; when contracted spicate, or more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets compressed laterally, or not noticeably compressed, or compressed dorsiventrally; disarticulating above the glumes; not disarticulating between the florets (or only tardily so). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present.

Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; pointed; awnless; carinate; similar (thinly membranous, acute or mucronate). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets reduced to a brush-like appendage.

Female-fertile florets (1–)3–5. Lemmas decidedly firmer than the glumes (leathery); not becoming indurated; incised; 13–23 lobed; deeply cleft (dissected above into awns); awned. Awns 13–23; median and lateral (spreading, unequal, together forming a pappus-like crown to the spikelet); the median similar in form to the laterals; non-geniculate; hairless to long-plumose; much longer than the body of the lemma (simple, or branched at the base). Lemmas hairy (at least below); non-carinate (dorsally rounded); without a germination flap; (5–)7–11 nerved (or more). Palea present; relatively long; apically notched; awnless, without apical setae; textured like the lemma (papyraceous); 2-nerved; 2-keeled. Palea keels wingless; scabrous to hairy. Lodicules present; 2; free; glabrous. Stamens 3. Ovary apically glabrous. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; ellipsoid; compressed dorsiventrally. Hilum short (1/5 as long as the grain). Pericarp fused. Embryo large. Endosperm hard; without lipid. Embryo with an epiblast; with a scutellar tail; with an elongated 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 (the costals relatively long and narrow); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type (and demonstrated to secrete salt). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (27–)28.5–30 microns long. Microhair basal cells 18 microns long. Microhairs 14.4–16.5 microns wide at the septum. Microhair total length/width at septum 1.7–2. Microhair apical cells 10.5–13.5 microns long. Microhair apical cell/total length ratio 0.35–0.45. Stomata common; 25.5–31.5 microns long. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary). Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped (the commonest form), or ‘panicoid-type’ (common in places); when panicoid type, cross shaped and butterfly shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 1, or 2–3. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (seemingly, occasionally). Leaf blade with distinct, prominent adaxial ribs, or ‘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; associated with colourless mesophyll cells to form deeply-penetrating fans (these sometimes connecting with traversing colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.

Special diagnostic feature. Spikelets with the distal incomplete florets and/or the rachilla apex forming a terminal clavate appendage.

Cytology. Chromosome base number, x = 10. 2n = 40, or 60, or 100. 4, 6, and 10 ploid. Nucleoli persistent.

Classification. Watson & Dallwitz (1994): Chloridoideae; Pappophoreae, or main chloridoid assemblage (relationships dubious). Soreng et al. (2015): Chloridoideae; Cynodonteae; Pappophorinae. 8 species.

Distribution, phytogeography, ecology. U.S.A., South America.

Xerophytic; species of open habitats. Grassland and bushland.

Rusts and smuts. Rusts — Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.

References, etc. Morphological/taxonomic: Reeder 1965; Reeder and Toolin 1989. Leaf anatomical: Metcalfe 1960; this project.

Illustrations. • P. philippianum: P. Beauv. (1812). • P. pappiferum, as polystachyum: Kunth (1835). • P. mucronulatum: Hitchcock and Chase (1950)


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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’.

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