| # The grass genera of the world |

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

### Pseudostachyum Munro

~ Schizostachyum

Habit, vegetative morphology. Perennial; rhizomatous. The flowering culms leafy. Culms 500–1600 cm high; woody and persistent; to 2.5 cm in diameter; scandent (above), or not scandent; branched above (near their tops). The branching dendroid. Culm leaf sheaths present; conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades triangular. Culm internodes hollow (the walls thin). Rhizomes culms arising singly from long creeping rhizome. Plants unarmed. Leaves not basally aggregated; with auricular setae (but these deciduous). Leaf blades lanceolate to elliptic (ending in a long, twisted, scabrous point); broad; 20–45 mm wide (8–30 cm long); not cordate, not sagittate (but asymmetric at the base); pseudopetiolate (the ‘petiole’ rather long, thick); cross veined; disarticulating from the sheaths; rolled in bud. Ligule present; short.

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

Inflorescence. Inflorescence indeterminate; with pseudospikelets; paniculate (large, with drooping branches); non-digitate; spatheate (the panicle leafy, the units bracteate); a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes ‘racemes’, or spikelike, or paniculate; persistent. Spikelets not secund; seemingly sessile and pedicellate.

Female-fertile spikelets. Spikelets 5 mm long; ovate; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes one per spikelet; shorter than the adjacent lemmas; hairless; mucronate; awnless. Upper glume 7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped (the terminal rachilla bearing glumes or an imperfect floret).

Female-fertile florets 1. Lemmas similar in texture to the glumes (and similar in form); not becoming indurated; mucronate; usually finely ciliate above. Palea present; relatively long; convolute around the flower; not indurated (thin); 2-keeled (the keels ciliate). Lodicules present (large, persistent); 3–5; free; membranous; ciliate; not toothed (acute, rounded or truncate); heavily vascularized. Stamens 6. Anthers with the connective apically prolonged (apiculate). Ovary apically glabrous; with a conspicuous apical appendage. The appendage long, stiff and tapering. Styles fused (into one long, rigid style). Stigmas 2 (short).

Fruit, embryo and seedling. Fruit fruit supported by persistent glume, lemma, palea and lodicules. Pericarp thick and hard (crustaceous); free.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (and small - not seen elsewhere). Mid-intercostal long-cells having markedly sinuous walls (thin). Microhairs present; panicoid-type. Stomata common (obscured by papillae). Subsidiaries probably low dome-shaped. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies saddle shaped (narrower than the costals), or tall-and-narrow. Costal short-cells predominantly paired (plus a few short rows). Costal silica bodies saddle shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with arm cells; with fusoids (large). Leaf blade adaxially flat (except near midrib). 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 (with all the bundles); forming ‘figures’ (in many bundles).

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): Bambusoideae; Bambusodae; Bambuseae; Melocanninae. 1 species (P. polymorphum).

Distribution, phytogeography, ecology. Eastern Himalaya, Assam and Upper Burma.

Shade species. Under large trees.

References, etc. Leaf anatomical: Metcalfe 1960.

Special comments. Fruit data wanting.

Illustrations. • Pseudostachyum polymorphum, with Puelia ciliata and Melocalamus compactiflorus (Camus, 1913). • Abbreviations for Camus (1913) figures. • Pseudostachyum polymorphum and Racemobambos prainii: Yun nan zhi wuxhi(2003).

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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