The grass genera of the world
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)
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’.