Oryzidium C.E. Hubb. & Schweick.
Habit, vegetative morphology. Floating perennial; stoloniferous. Culms 40–120 cm high (the lower internodes trailing in water or floating); herbaceous (spongy); branched above. Culm nodes glabrous. Culm sheaths persistent (even when permanently submerged). Culm internodes solid (spongy). Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 6–10 mm wide; flat; without cross venation; persistent; a fringe of hairs; 3–4 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; without hermaphrodite florets (the lower floret male, the upper female).
Inflorescence. Inflorescence paniculate; narrow, the branches nearly erect; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate; somewhat imbricate.
Female-fertile spikelets. Spikelets 8–10 mm long; lanceolate; compressed dorsiventrally; biconvex; falling with the glumes; not disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (i.e., the upper floret stipitate). Rachilla terminated by a female-fertile floret; hairless. Hairy callus absent.
Glumes two; very unequal; (the upper) long relative to the adjacent lemmas; hairless; glabrous (G1), or scabrous (G2, on the veins); (the upper) awned (attenuate into a long straight awn); non-carinate; very dissimilar (the G1 a small, membranous, truncate scale, the G2 large, firm, awned). Lower glume shorter than the lowest lemma; 0 nerved, or 3 nerved (faint). Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed; not becoming conspicuously hardened and enlarged laterally. The proximal incomplete florets male (with 3 stamens). The proximal lemmas acuminate; awned (attenuate); 5 nerved; decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (thinly leathery); smooth; not becoming indurated; entire; pointed; mucronate (or mucronulate); hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 7 nerved. Palea present; relatively long; tightly clasped by the lemma; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 0 (the male floret with non-penicillate anthers 2.5–3 mm long). Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea (but clasped below by the flaps of the palea); small (3–3.5 mm long); ellipsoid; compressed dorsiventrally. Hilum short. Embryo large; not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (72–)75–84(–90) microns long; (4.8–)5.7–6 microns wide at the septum. Microhair total length/width at septum 12–18.8. Microhair apical cells (46–)51–56(–57) microns long. Microhair apical cell/total length ratio 0.63–0.68. Stomata common (easy to find, but thinly spread); 27–33 microns long. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells conspicuously in long rows (some veins), or predominantly paired (some veins), or neither distinctly grouped into long rows nor predominantly paired (some veins). Costal silica bodies ‘panicoid-type’; all very small, dumb-bell shaped and nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS+. PCR sheath outlines even. PCR cell chloroplasts seemingly centripetal. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous (with a large air-space on either side of the large bundle); having a conventional arc of bundles (one large bundle, two small); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 1 species; southern tropical Africa. Hydrophytic (in permanent water); species of open habitats; glycophytic.
Paleotropical. African. Sudano-Angolan and Namib-Karoo. Kalaharian.
References, etc. Morphological/taxonomic: Hubbard and Schweickerdt 1936. Leaf anatomical: this project; photos of O. barnardii provided by R.P. Ellis.
Illustrations. • General aspect. • Lemma and palea. Oryzidium barnardii. Leathery fertile lemma with margins lying flat and exposed on the similarly textured palea. • Leaf blade transverse section. • Leaf blade transverse section
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
