Ottochloa Dandy
Named for Otto Stapf, distinguished agrostologist.
Including Hemigymnia Stapf
Habit, vegetative morphology. Perennial; decumbent (slender). Culms herbaceous. Culm nodes glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; broad, or narrow; flat (thin); pseudopetiolate, or not pseudopetiolate; cross veined, or without cross venation; tardily disarticulating from the sheaths; rolled in bud; an unfringed membrane to a fringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (the branches weakly unilateral, with appressed secondary racemelets), or a single raceme; open; with capillary branchlets; non-digitate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; not secund; pedicellate (the pedicels widened upwards). Pedicel apices cupuliform.
Female-fertile spikelets. Spikelets 1.7–6.4 mm long; elliptic; abaxial or not orientated; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; two; very unequal (O. grandiflora), or more or less equal; shorter than the spikelets (about 1/2 to 2/3 as long), or about equalling the spikelets (O. grandiflora); shorter than the adjacent lemmas (except in O. grandiflora); hairless (usually glabrous); pointed, or not pointed; awnless; similar (membranous). Lower glume 3–5 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 5–7 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (subleathery); smooth to striate; becoming indurated to not becoming indurated; yellow in fruit; entire; pointed; awnless to mucronate (or rather, apiculate to mucronulate); hairless; non-carinate; having the margins lying flat on the palea (O. grandiflora), or having the margins inrolled against the palea; with a clear germination flap; 3 nerved, or 5 nerved. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit small; compressed dorsiventrally (strongly). Hilum short. Embryo large; not waisted.
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 (the costals slightly thicker walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 39–69 microns long; 5–8.4 microns wide at the septum. Microhair total length/width at septum 6.5–10. Microhair apical cells 21–36 microns long. Microhair apical cell/total length ratio 0.48–0.62. Stomata common; 24–37.5 microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs, or not paired (solitary); silicified, or not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings.
Special diagnostic feature. Plants not as in Dichanthelium (q.v.).
Cytology. Chromosome base number, x = 9. 2n = 18. 2 ploid.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 5 species; Africa, Indomalayan region, Australia. Shade species and species of open habitats. Damp and shady places.
Paleotropical and Australian. African, Indomalesian, and Neocaledonian. West African Rainforest. Indian, Indo-Chinese, Malesian, and Papuan. North and East Australian. Tropical North and East Australian.
Rusts and smuts. Rusts — Physopella and Puccinia. Taxonomically wide-ranging species: Physopella clemensiae, Puccinia orientalis, and ‘Uromyces’ setariae-italicae.
Economic importance. Significant weed species: O. nodosa.
References, etc. Leaf anatomical: this project.
Special comments. The morphological description incorporates corrections forwarded by J.F. Veldkamp (1997), who draws attention to peculiarities of the Malesian species, O. grandiflora.
Illustrations. • Abaxial epidermis of leaf blade. • Transverse section of leaf blade
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).
