| # The grass genera of the world |

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

### Vietnamochloa Veldkamp & Nowack

From the Greek chloa (grass) and geography.

Habit, vegetative morphology. Annual; caespitose. Culms 25 cm high; herbaceous; unbranched above. Leaves mostly basal. Leaf blades linear; 1.5–2 mm wide; flat, or rolled; not needle-like; without abaxial multicellular glands; not pseudopetiolate. Ligule a fringe of hairs.

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

Inflorescence. Inflorescence paniculate; non-digitate; espatheate. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate; not imbricate.

Female-fertile spikelets. Spikelets 4–4.25 mm long; fusiform; compressed dorsiventrally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension naked. Hairy callus present.

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; hairless; glabrous; pointed; awnless; carinate; similar. Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas similar in texture to the glumes; entire; not deeply cleft; awned. Awns not of the triple/trifid, basal column type; 1; median; non-geniculate; much shorter than the body of the lemma. Lemmas hairy; non-carinate; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; 2-nerved. Palea back hairy. Stamens 3. Anthers 1.5 mm long. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally; smooth. Hilum short. Pericarp thin; fused. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (broader intercostally); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (irregular). Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall thinner than that of the basal cell but not tending to collapse. Microhairs 24–30 microns long. Microhair basal cells 18–21 microns long. Microhairs 6 microns wide at the septum. Microhair total length/width at septum 6. Microhair apical cells 9–12 microns long. Microhair apical cell/total length ratio 0.3. Stomata common; 15 microns long. Subsidiaries non-papillate; dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (few); mostly in cork/silica-cell pairs (when present); silicified (few). Intercostal silica bodies present and perfectly developed (but few); tall-and-narrow. Prickles and macrohairs present only on the leaf margins. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; present in alternate cell files of the costal zones; saddle shaped.

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

C4. The anatomical organization conventional. XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. Mesophyll without adaxial palisade. Leaf blade adaxially flat (but abaxially ribbed). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (middle cell very large and deeply penetrating the chlorenchyma). All the vascular bundles accompanied by sclerenchyma. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres (large).

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 1 species (V. aurea).

Distribution, phytogeography, ecology. Vietnam.

References, etc. Morphological/taxonomic: Nowack and Veldkamp 1994. Leaf anatomical: Van den Borre 1994.

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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