Oxytenanthera Munro
Including Houzeaubambus Mattei, Scirpobambus Kuntze
Sometimes referred to Dendrocalamus
Habit, vegetative morphology. Arborescent shrubby perennial; caespitose. The flowering culms leafy (but the culm leaves deciduous). Culms 300–1300 cm high (somewhat crooked, bending over to the ground); woody and persistent (forming dense clumps); to 10 cm in diameter; cylindrical; branched above (at the nodal line). Culm nodes glabrous. Primary branches/mid-culm node 1 (with subsidiary branches from these forming clusters). Culm sheaths persistent. Culm internodes solid, or hollow. Pluricaespitose. Rhizomes pachymorph. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate; with auricular setae (these deciduous). Leaf blades linear-lanceolate to lanceolate; broad; 10–30 mm wide; flat; pseudopetiolate; without cross venation; disarticulating from the sheaths; an unfringed membrane; truncate; 0.3–0.5 mm long. Contra-ligule present.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (there being numerous sterile spikelets); hermaphrodite and sterile.
Inflorescence. Inflorescence indeterminate; with pseudospikelets; a false spike, with spikelets on contracted axes (the clusters sometimes confluent or reduced to a single terminal cluster like that of female Spinifex); spatheate (each spikelet cluster subtended by a papery sheath, and individual spikelets by several short, papery ‘bracts’); not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes capitate. Spikelets associated with bractiform involucres.
Female-fertile spikelets. Spikelets 15–45 mm long; compressed laterally to not noticeably compressed; falling with the glumes; not disarticulating between the florets. Rachilla terminated by a female-fertile floret; hairless. Hairy callus absent.
Glumes two (cross-veined); very unequal; shorter than the adjacent lemmas; hairy (shortly hispidulous); pointed, or not pointed (obtuse to acute); awnless; non-carinate; similar (papery to leathery). Lower glume much shorter than half length of lowest lemma; 17–30 nerved. Upper glume 17–30 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1–3; male, or sterile (the paleas when present two-keeled). The proximal lemmas awned, or awnless (then mucronate); 26–32 nerved; exceeded by 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 (papery to thinly leathery); not becoming indurated; entire; pointed; mucronate to awned. Awns 1; median; apical; non-geniculate; to 7 mm long. Lemmas hairy (hispid); non-carinate; without a germination flap; 11–23 nerved (with cross-nerves). Palea present; relatively long (may exceed the lemma); entire (pointed); awnless, without apical setae; not indurated; several nerved (16–19); keel-less (convolute). Lodicules absent. Stamens 6; monadelphous. Anthers not penicillate; with the connective apically prolonged. Ovary glabrous (but the style mostly shortly hairy); with a conspicuous apical appendage. The appendage long, stiff and tapering. Styles fused (the ovary attenuate into the single, hollow style). Stigmas 3.
Fruit, embryo and seedling. Fruit free from both lemma and palea; large; not noticeably compressed. Hilum long-linear. Embryo small. Endosperm containing compound starch grains.
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 over-arching the stomata; several per cell. Long-cells markedly different in shape costally and intercostally; differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; 42–46.5 microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 7–8.8. Microhair apical cells 21–24 microns long. Microhair apical cell/total length ratio 0.45–0.52. Stomata common; 27–30 microns long. Subsidiaries low to high dome-shaped, or triangular. Intercostal short-cells absent or very rare. Costal short-cells predominantly paired. Costal silica bodies saddle shaped and oryzoid; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; having complex vascularization. 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.
Cytology. Chromosome base number, x = 12. 2n = 72. 6 ploid.
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 1 species; Africa. Mesophytic; shade species; glycophytic. Growing in the protection of larger trees.
Paleotropical. African. Sudano-Angolan and West African Rainforest. Sahelo-Sudanian, Somalo-Ethiopian, and South Tropical African.
Rusts and smuts. Rusts — Dasturella. Taxonomically wide-ranging species: Dasturella divina.
Economic importance. O. abyssinica stems used for light construction and fencing.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • General structure
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).
