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The grass genera of the world

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

Bergbambos Stapleton

~ Thamnocalamus tesselatus

Type species: Bergbambos tessellata (Nees) Stapleton.

Habit, vegetative morphology. Perennial; loosely clumped, () caespitose. Culms to 700 cm high; woody and persistent; to 2 cm in diameter; cylindrical; branched above. Buds from which the primary culm branches arise (where recorded) 1. The branching dendroid. Culm nodes without roots. Culm leaf sheaths present; persistent; not conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades lanceolate. Culm internodes hollow. Unicaespitose. Leaves auriculate to non-auriculate; with auricular setae. Leaf blades (acuminate-) lanceolate (with scabrous cartilaginous margins); broad; 5–15 cm long, 8–15 mm wide; with a prominent midrib, shortly pseudopetiolate. Ligule a fringed membrane; scarious, truncate; 1–1.5 mm long. Contra-ligule absent.

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

Inflorescence. Inflorescence determinate; without pseudospikelets; complexly paniculate (comprising compressed, racemose branches, to 40 cm long). Primary inflorescence branches numerous. Inflorescence spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes "comprising compact, bracteolate fascicles". Spikelets on the ultimate racemes, not secund; distichous; sessile.

Female-fertile spikelets. Spikelets 15.4–17.4 mm long; ovate; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.

Glumes two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas (the upper 1–1.3 times its length); non-carinate; lanceolate, chartaceous, similar. Lower glume 0.75 times the length of the upper glume; 9 nerved. Upper glume 9–13 nerved (the laterals with cross-veins). 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 characteristically 1. Lemmas oblong, 11–15 mm long; chartaceous, similar in texture to the glumes; not becoming indurated; entire; pointed (acute); awnless; non-carinate; 10 nerved, or 11 nerved; with the nerves confluent towards the tip. Palea present; relatively long (10–12.5 mm long); several nerved (11 nerved). Palea keels ciliolate. Lodicules present; 3; membranous (scarious); ciliate (and apically hairy); 1.8–2.4 mm long, oblong, not toothed. Stamens 3. Anthers orange, 7.2–8.5 mm long; not penicillate; without an apically prolonged connective. Ovary without a conspicuous apical appendage. Styles fused; completely fused. Stigmas 3.

Fruit, embryo and seedling. Pericarp fused.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae some over-arching the stomata; variously shaped. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhairs 55–70 microns long. Microhair basal cells 33–40 microns long. Microhair apical cells 22–29 microns long. Stomata common. Subsidiaries papillate; dome-shaped (often obscured by papillae). Intercostal short-cells common; in cork/silica-cell pairs and not paired. Intercostal silica bodies infrequent. Macrohairs infrequent abaxially, stiff with swollen constricted bases; prickle hairs infrequent, comprising hooks. Costal short-cells conspicuously in long rows (with some pairs). Costal silica bodies present and well developed; saddle shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with fusoids. Leaf blade more or less adaxially flat. Midrib conspicuous. 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’.

Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Bambusoideae; Bambusodae; Arundinarieae; Arundinariinae. 1 species (B. tessellata).

Distribution, phytogeography, ecology. Mountains of South Africa, Lesotho and Swaziland.

References, etc. Morphological/taxonomic: Stapleton, C.M.A. (1013). Bergbambos and Oldeania, new genera of African bamboos (Poaceae, Bambusoideae). PhytoKeys 25: 87–103; Clayton et al. (2016), Grassbase. Leaf anatomical: Metcalfe (1960).

Illustrations. • B. tessellata: Hook. Ic. Pl. (1913)

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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: 11th December 2017.’.