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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)

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.’.