The grass genera of the world
Type species: Type: P. dissectum (L.) L.
Including Anachyris Nees, Cerea Schlecht., Ceresia Pers., Cleachne Roland. ex Rottb., Cymotochloa Schlecht., Dichromus Schlecht., Digitaria Fabric., Dimorphostachys Fourn., Maizilla Schlecht., Moenchia Steud., Paspalanthium Desv., Reimaria Fluegge, Sabsab Adans., Spheneria, Wirtgenia Doell
Excluding Reimarochloa, Thrasya, Thrasyopsis
Habit, vegetative morphology. Perennial (usually), or annual; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–300 cm high (rarely taller, sometimes with culms trailing to 2 m or more); herbaceous; sparsely to amply branched above, or unbranched above. The branching simple. Culm nodes hairy, or glabrous. Culm leaf sheaths keeled, or rounded. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear, or linear to linear-lanceolate; broad, or narrow; (1–)3–25(–30) mm wide; flat, or folded, or rolled; without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane to a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants outbreeding, or inbreeding; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes when present, subterranean. Apomictic, or reproducing sexually.
Inflorescence. Inflorescence of spicate main branches; digitate, or subdigitate, or non-digitate. Primary inflorescence branches (1–)2–20(–60); inserted all around the main axis. Inflorescence with axes ending in spikelets (usually), or axes not ending in spikelets (rachides naked-tipped in (e.g.) P. repens). Rachides hollowed, or flattened, or winged (narrow to broadly foliaceous or membranous). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating (e.g., P. repens), or persistent; when disarticulating falling entire. Spikelets solitary, or paired; secund (on unilateral rachides); biseriate (or in 3 or four rows); subsessile, or pedicellate. Pedicel apices oblique, or truncate, or discoid, or cupuliform. Spikelets consistently in long-and-short combinations, or not in distinct long-and-short combinations; when in long/short pairs unequally pedicellate in each combination. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets (1.2–)1.5–4.2(–4.5) mm long; suborbicular, or elliptic, or lanceolate, or ovate, or obovate; abaxial; compressed dorsiventrally; (concavo- to) planoconvex; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present (usually), or absent (in Section Anachyris); when present, one per spikelet (in species with an andropogonoid spikelet arrangement), or two; very unequal; (the upper) long relative to the adjacent lemmas; free; dorsiventral to the rachis; awnless; very dissimilar (the G1 usually much reduced). Lower glume 0–1 nerved. Upper glume 3–6 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 3–5 nerved (usually), or 2 nerved (P. ceresia); more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas apiculate; similar in texture to the glumes to decidedly firmer than the glumes (papery to crustaceous); smooth to striate; becoming indurated to not becoming indurated; yellow in fruit, or brown in fruit; entire; blunt; awnless; hairless; non-carinate; having the margins inrolled against the palea; with a clear germination flap; 3–5 nerved. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma (usually glossy); indurated, or not indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large, or small (rarely). Endosperm hard; without lipid; containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad; curved.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; ostensibly one-celled (the basal cell sometimes completely embedded), or clearly two-celled; panicoid-type; (28–)34–45(–46.5) microns long; 5.7–6.3 microns wide at the septum. Microhair total length/width at septum 6.2–6.4. Microhair apical cells 12–30 microns long. Microhair apical cell/total length ratio when applicable 0.49–0.62. Stomata common; (30–)31–36(–42) microns long. Subsidiaries low dome-shaped and triangular, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; in cork/silica-cell pairs (usually), or not paired (a few solitaries); silicified (when paired). Intercostal silica bodies imperfectly developed; when present, cross-shaped, or cross-shaped and vertically elongated-nodular. Costal short-cells conspicuously in long rows. Costal silica bodies present throughout the costal zones, or confined to the central file(s) of the costal zones to present in alternate cell files of the costal zones; panicoid-type; cross shaped to dumb-bell shaped, or nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NADPME (P. notatum, P. dilatatum); XyMS. PCR sheath outlines uneven. PCR sheath extensions absent. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially, or without colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (sometimes irregularly grouped); often in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres (large).
Culm anatomy. Culm internode bundles in three or more rings.
Phytochemistry. Tissues of the culm bases with abundant starch. Leaves containing flavonoid sulphates (2 species), or without flavonoid sulphates (2 species).
Special diagnostic feature. Spikelets awnless, muticous.
Cytology. Chromosome base number, x = 10 and 12. 2n = 20, 40, 48, 50, 60, 63, and 80. 2, 4, and 6 ploid. Chromosomes small. Mean diploid 2c DNA value 1.6 pg (2 species of unknown ploidy, 1.2 and 2.1). Nucleoli persistent.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 320 species.
Distribution, phytogeography, ecology. In warm regions.
Commonly adventive. Mostly helophytic, or mesophytic, or xerophytic; mostly species of open habitats; halophytic (a few, e.g. P. distichum), or glycophytic. In diverse habitats - savanna, damp places, forest margins, weedy ground, coastal sands (including useful sandbinders), coastal and inland saltmarshes.
Economic aspects. Significant weed species: P. ciliatifolium, P. conjugatum, P. dilatatum, P. fimbriatum, P. fluitans, P. laeve, P. lividum, P. longifolium, P. notatum, P. paspaloides, P. plicatulum, P. scrobiculatum, P. thunbergii, P. urvillei, P. vaginatum, P. virgatum. Cultivated fodder: P. dilatatum (Dallis), P. notatum (Bahia), P. plicatulum. Important native pasture species: several, e.g. P. auriculatum, P. glumaceum, P. notatum, P. paniculatum, P. scrobiculatum. Grain crop species: P. scrobiculatum (Kodo - India).
Rusts and smuts. Rusts Physopella and Puccinia. Taxonomically wide-ranging species: Puccinia chaetochloae, Puccinia dolosa, Puccinia levis, Puccinia substriata, Puccinia emaculata, Puccinia coronata, and Puccinia esclavensis. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Tilletia. Ustilaginaceae Sorosporium, Sphacelotheca, Tolyposporium, and Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us - P. conjugatum Berg., P. dilatatum Poiret, P. distichum L., P. vaginatum Swartz.
Illustrations. • P. inaequivalve: Kunth (1835). • P. scrobiculatum: Gardner, 1952. • P. scrobiculatum: Fl. W. Trop. Afr. (1936). • P. orbiculatum, as P. pusillum: Kunth (1835). • General aspect (P. dilatatum): Gibbs Russell et al., 1990. • Inflorescence and spikelet (P. dilatatum): E. Hickman. • Ligule region (P. dilatatum). • Inflorescence of P. distichum. • ‘Front’ of axis with 2-ranked spikelets (P. distichum). • Inflorescence detail (P. notatum). • ‘Front’ of axis of P. notatum inflorescence. • ‘Back’ of axis of P. dilatatum. • ‘Front’ of axis, spikelets 4-ranked (P. dilatatum). • Detail of old inflorescence (P. dilatatum). • Exposed female-fertile floret in close-up (P. notatum). • Palea and flower of P. dilatatum. • Transverse section of leaf blade (P. dilatatum). • Pollen antigens: Watson and Knox (1976). • Pollen antigens: cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Lolium serum. • Heat stable pollen antigens (allergens): cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Cynodon serum. • Pollen antigens: cross-reactions against anti-Zea serum. • Pollen antigens: cross-reactions against anti-Zea serum
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. delta-intkey.com/grass’.