The grass genera of the world
Including Mapira Adans.
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy. Culms 50–500 cm high; woody and persistent; scandent (twining), or not scandent; self-supporting, or scrambling, or scandent; usually sparsely branched above. The branching simple. Culm nodes hairy, or glabrous. Culm internodes hollow. Leaves not basally aggregated; auriculate, or non-auriculate; without auricular setae. Leaf blades lanceolate to ovate; broad; (12–)30–130 mm wide; cordate (sometimes basally asymmetric), or sagittate; flat; pseudopetiolate; cross veined (these rarely inconspicuous?); disarticulating from the sheaths; rolled in bud. Ligule an unfringed membrane, or a fringed membrane; truncate. Contra-ligule absent.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual (the male spikelets immediately beneath the females, or the lower parts of the panicle exclusively male); without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets on different branches of the same inflorescence, or segregated, in different parts of the same inflorescence branch (female spikelets terminating the branches, the smaller male spikelets below, or the upper branches all female, the lower all male). The spikelets overtly heteromorphic.
Inflorescence. Inflorescence determinate, or indeterminate (?synflorescences); paniculate; open, or contracted; spatheate, or espatheate (?); a complex of partial inflorescences and intervening foliar organs (spatheolate synflorescences), or not comprising partial inflorescences and foliar organs (?). Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate (female spikelets on stout, clavate peduncles, males on slender pedicels).
Female-sterile spikelets. The male spikelets usually shorter than the females; without glumes; stamens 3, free. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 3 staminate. The staminal filaments free.
Female-fertile spikelets. Spikelets (5.5–)7–50 mm long; elliptic, or ovate; compressed dorsiventrally; nearly always disarticulating above the glumes (the glumes persistent, except in O. micrantha); with conventional internode spacings, or with a distinctly elongated rachilla internode above the glumes. The upper floret conspicuously stipitate, or the upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes two; very unequal (the lower longer), or more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; not ventricose (by contrast with Parodiolyra); hairy to hairless; pointed (acuminate to aristate); awnless, or awned (often caudate-acuminate); non-carinate; similar (papery or herbaceous, often with transverse veinlets). Lower glume 5–15 nerved. Upper glume (3–)5–11 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1 (the anthecium recalling that of Paniceae). Lemmas finally decidedly firmer than the glumes; becoming indurated; entire; blunt; awnless; hairy, or hairless; non-carinate; having the margins inrolled against the palea; with a clear germination flap. Palea present; relatively long; tightly clasped by the lemma; entire; awnless, without apical setae; indurated; 2-nerved, or several nerved (2–4); keel-less. Lodicules present; 3; free; membranous; glabrous; heavily vascularized. Stamens 0. Ovary apically glabrous. Styles fused (into one); completely fused. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small to medium sized (3.8–9 mm long); fusiform, or ellipsoid; compressed dorsiventrally, or not noticeably compressed. Hilum long-linear (as long as the caryopsis). Embryo small (a fifth or less of the caryopsis length). Endosperm hard; without lipid. Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a short mesocotyl; with a loose coleoptile. First seedling leaf without a lamina.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; several per cell (most long-cells and interstomatals with one or two rows of smallish, round papillae in O. latifolia). Intercostal zones with typical long-cells (though these rather short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (48–)51–72(–77) microns long; (3.6–)3.9–4.2(–5.4) microns wide at the septum. Microhair total length/width at septum 10.6–13.3. Microhair apical cells 19.5–21–36 microns long. Microhair apical cell/total length ratio 0.39–0.45. Stomata common; 21–25.5 microns long. Subsidiaries predominantly triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies vertically elongated-nodular. Costal short-cells conspicuously in long rows. Costal silica bodies saddle shaped (common over some veins, in O. latifolia), or oryzoid, or panicoid-type; in O. latifolia commonly plump cross shaped and butterfly shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous (adaxial and abaxial projections); with one bundle only, or having a conventional arc of bundles, or having complex vascularization. Bulliforms present in discrete, regular adaxial groups; in simple fans (the fans wide). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaves without flavonoid sulphates (O. latifolia).
Cytology. 2n = 14, 20, 22, 30, 40, and 44.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 23 species.
Distribution, phytogeography, ecology. Tropical America, Africa.
Commonly adventive. Mesophytic; shade species; glycophytic. In forests.
Rusts and smuts. Rusts Physopella and Puccinia.
References, etc. Morphological/taxonomic: Soderstrom and Zuloaga 1989. Leaf anatomical: Metcalfe 1960; studied by us - O. latifolia L.
Illustrations. • O. latifolia: Fl. W. Trop. Afr. (1936). • General aspect (O. latifolia): Gibbs Russell et al., 1990. • O. latifolia, abaxial epidermis of leaf blade: this project
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’.