| # The grass genera of the world |

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

### Pleioblastus Nakai

~ Arundinaria

Habit, vegetative morphology. Perennial; nearly always rhizomatous. The flowering culms leafy. Culms 20–800 cm high; woody and persistent (sometimes with aerial roots from the nodes); cylindrical (often supranodally ridged); branched above (usually), or unbranched above. Primary branches when present, 1, or 2, or 3, or 4–10 (to ‘many’, or ‘sparse’, variously subequal or having one dominant). The branching suffrutescent, or dendroid (usually). Culm leaf sheaths present; deciduous, or persistent; leaving a persisten girdle; conspicuously auriculate, or not conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades linear, or lanceolate, or ovate, or triangular. Rhizomes leptomorph. Leaves auriculate (rarely, then erect or falcate), or non-auriculate; with auricular setae, or without auricular setae. Leaf blades herbaceous, chartaceous or leathery, linear, or linear-lanceolate, or lanceolate (nearly always), or ovate, or elliptic; pseudopetiolate; cross veined, or without cross venation; disarticulating from the sheaths, or persistent. Ligule present; an unfringed membrane, or an unfringed membrane to a fringed membrane. Contra-ligule absent.

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

Inflorescence. Inflorescence determinate; without pseudospikelets; few spikeleted, or many spikeleted (?); terminal or terminal and acillary, of spicate main branches, or paniculate (? - see the incomprehensible Clayton et al. description); more or less spatheate (subtended by an unspecialised sheath or a spatheole); not comprising ‘partial inflorescences’ and foliar organs (?). Spikelets solitary; pedicellate.

Female-fertile spikelets. Spikelets morphologically ‘conventional’ to unconventional; 24.9–110 mm long; usually linear; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets.

Glumes chartaceous, persistent, one per spikelet, or one per spikelet to two (the presence of the lower commonly variable among the spikelets), or several (to ‘several’); much shorter than the spikelets; shorter than the adjacent lemmas; pointed; acute to attenuate awnless; non-carinate. Upper glume 5–11 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless.

Female-fertile florets 4–15. Lemmas lanceolate to elliptic or ovate; chartaceous, similar in texture to the glumes; smooth; not becoming indurated; entire; pointed; acute or more often acuminate, awnless (usually), or mucronate; having the margins sometimes ciliolate, otherwise hairless; non-carinate. Palea present; relatively long (about equalling the lemma); not convolute (?); entire, or apically notched; awnless, without apical setae to with apical setae (sometimes with excurrent veins); 1-nerved, or several nerved; 2-keeled. Palea back glabrous to hairy. Palea keels glabrous, or hairy. Lodicules present; 3; membranous; ciliate, or glabrous; not toothed. Stamens 3. Ovary apically glabrous; presumably without a conspicuous apical appendage (?). Stigmas 2.

Fruit, embryo and seedling. Fruit medium sized to large (1–1.2 cm long); apically unappendaged; longitudinally grooved. Hilum long-linear. Pericarp thin; fused. Embryo small. Endosperm hard; without lipid.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata, or not over-arching the stomata; several per cell (in one or more rows per cell). Mid-intercostal long-cells having markedly sinuous walls (these thin). Microhairs present; panicoid-type (distal cells often variable in shape). Stomata common. Subsidiaries low to high dome-shaped (usually), or triangular (rarely). Intercostal short-cells common, or absent or very rare; in cork/silica-cell pairs; silicified, or not silicified. Intercostal silica bodies when present, often tall-and-narrow, or vertically elongated-nodular. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired, or conspicuously in long rows (sometimes, over main veins). Costal silica bodies saddle shaped (commonly), or oryzoid to ‘panicoid-type’ (sometimes tending to cross-shaped, then sometimes tending to be vertically elongated).

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size, or with the ribs very irregular in sizes. Midrib conspicuous; having complex vascularization. The lamina distinctly asymmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (mostly), or in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): genus not recognised. Soreng et al. (2015): Bambusoideae; Arundinarodae; Arundinarieae; Arundinariinae. About 30 species.

Distribution, phytogeography, ecology. Mostly temperate Asia, but represented in Europe, tropical Asia, Australasia and the Pacific.

References, etc. Leaf anatomical: Metcalfe (1960), as 5 Arundinaria spp.

Special comments. Fruit data wanting.

Illustrations. • Pleioblastus simonii (as Arundinaria simonii var. variegata): Bot. Mag. 116 (1890). • Pleioblastus viridistriatus, as Arundinaria auricoma: Hook. Ic. Pl. 27 (1901). • Pleioblastus viridistriatus and P. fortunei (as Arundinaria spp.: Camus, 1913). • Abbreviations for Camus (1913) figures. • Pleioblastus simoni and P. argenteostriatus (as Arundinaria simoni and A. chinolaydekeri): Camus (1913). • abbreviations for Camus (1913) figures. • Pleioblastus fortunei, as Arundinaria variegata: Nicora & Rúgolo de Agrasar (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: 15th June 2025. delta-intkey.com’.

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