The grass genera of the world
Habit, vegetative morphology. Arborescent perennial. The flowering culms leafy. Culms 450–1800 cm high; woody and persistent; to 10 cm in diameter; branched above. Primary branches 2, or 3; in an irregular line. The branching dendroid. Culm nodes glabrous. Culm leaf sheaths present; not conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades linear. Culm internodes hollow. Pluricaespitose. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; without auricular setae. Leaf blades lanceolate to elliptic; broad; 25–60 mm wide; pseudopetiolate; without cross venation; disarticulating from the sheaths; rolled in bud.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. Not viviparous.
Inflorescence. Inflorescence indeterminate; with pseudospikelets; a false spike, with spikelets on contracted axes (with involucrate, cupuliform clusters of pseudospikelets on bare branches); spatheate (each cluster subtended by a deciduous spathe, and associated with broad, leathery bracts). Spikelet-bearing axes very much reduced (the spikelet clusters of 3 or more spikelets or pseudo-spikelets each subtended by a pair of leafy bracts); persistent. Spikelets associated with bractiform involucres.
Female-fertile spikelets. Spikelets unconventional; 12–15 mm long; lanceolate; compressed laterally to not noticeably compressed; falling with the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension naked. Hairy callus absent.
Glumes one per spikelet; long relative to the adjacent lemmas; hairless (papery); glabrous; not pointed; awnless; non-carinate. Upper glume 11–18 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 2 (subequal). Lemmas similar in texture to the glumes to decidedly firmer than the glumes (papery to thinly leathery); not becoming indurated; entire; blunt; awnless; hairless; glabrous; without a germination flap; 11–23 nerved. Palea present; relatively long; not convolute; apically notched; awnless, without apical setae; not indurated; several nerved (5–11); 2-keeled. Lodicules absent. Stamens 6. Anthers not penicillate; with the connective apically prolonged. Ovary apically hairy; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused (into one). Stigmas 1.
Fruit, embryo and seedling. Pericarp thick and hard; free (and with a crustaceous, hairy apical appendage).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell. Long-cells similar 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. Stomata common (obscured by papillae). Subsidiaries dome-shaped, or triangular (?-outlines obscure). Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells predominantly paired. Costal silica bodies saddle shaped (rather variable); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with arm cells; with fusoids. Leaf blade adaxially flat. 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.
Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): cf. Bambusoideae (as a synonym?); Bambusodae; Bambuseae; Bambusinae. 1 species (O. buchwaldii).
Distribution, phytogeography, ecology. Tropical East Africa.
References, etc. Leaf anatomical: Metcalfe 1960.
Special comments. Fruit data wanting. Illustrations. • O. buchwaldii: Ibrahim & Kabuye, Kenya Grasses (1987)
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’.