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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Oldeania Stapleton

~ Arundinaria, Sinarundinaria, Yushania

Type species: Oldeania alpina (K. Schum.) Stapleton.

Habit, vegetative morphology. Culms erect to nodding, 1500–2000 cm high; to 12 cm in diameter; cylindrical to flattened on one side (with a shallow sulcus above the nodes); not scandent; branched above. Primary branches 3–10; in an irregular line. The branching dendroid. Culms often with thornlike aerial roots. Culm leaf sheaths present; conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades linear. Culm internodes hollow (with a small lumen). Rhizomes long-necked pachymorph. Leaves auriculate; with auricular setae. Leaf blades lanceolate (attenuate-filiform); broad to narrow; 5–20 cm long, 6–15 mm wide; pseudopetiolate; cross veined; disarticulating from the sheaths. Ligule an unfringed membrane. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence synflorescences) determinate; with pseudospikelets (with two empty glumes with or without bud remnants, and 4–8 fertile ones); paniculate; 5–15 cm long, open; elliptic. Spikelets solitary; pedicellate (the pedicels "scabrous" or "glabrous", depending on where one looks in Stapleton’s (2013) paper).

Female-fertile spikelets. Spikelets unconventional; 3–4 mm wide, 15–40 mm long; linear; compressed laterally, or compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present.

Glumes two; very unequal to more or less equal; much shorter than the spikelets; shorter than the adjacent lemmas; hairless; pointed (acuminate); awnless; non-carinate; herbaceous, ovate or elliptic, similar. Lower glume about 0.8 times the length of the upper glume; shorter than the lowest lemma; relatively smooth; 5–9 nerved. Upper glume 5–9 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless. Spikelets without proximal incomplete florets.

Female-fertile florets 2–7 ("to several", according to Stapleton), or 5–10 (Clayton et al.). Lemmas ovate; herbaceous, cross-veined, 7–10 mm long, similar in texture to the glumes; smooth; not becoming indurated; entire; pointed (acute); awnless; hairless; non-carinate. Palea present; relatively long (equalling the lemma); not convolute; tightly clasped by the lemma; awnless, without apical setae; 2-nerved; 2-keeled (sulcate between them to accommodate the racheole). Palea back glabrous. Palea keels ciliolate. Lodicules present; 3; joined; membranous; ciliate; obovate, slightly toothed to not toothed. Stamens 3; with free filaments. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous; without a conspicuous apical appendage. Stigmas 2 (mostly), or 3.

Fruit, embryo and seedling. Fruit ellipsoid to subglobose; longitudinally grooved; glabrous; smooth. Hilum long-linear. Pericarp fused. Embryo small.

Abaxial leaf blade epidermis. Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Stomata common. Subsidiaries papillate; dome-shaped. Intercostal short-cells common.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

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; having complex vascularization; without colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (I’s and T’s). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Bambusoideae; Arundinarodae; Arundinariinae. 1 species (O. alpina).

Distribution, phytogeography, ecology. Tropical Africa from Cameroon in the west to E. Africa, from Ethiopia south to Tanzania.

References, etc. Morphological/taxonomic: Stapleton, C.M.A. (2013). Bergbambos and Oldeania, new genera of African bamboos (Poaceae, Bambusoideae). PhytoKeys 25: 87–103; Clayton et al (2016), Grassbase. Leaf anatomical: Jacques-Félix (1962).

Illustrations. • O. alpina, spikelet (Jacques-Félix, 1962). • O. alpina, leaf blade anatomy (Jacques-Félix, 1962)


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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: 13th November 2017. delta-intkey.com/grass’.

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