| # The grass genera of the world |

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

### Lepturopetium Morat

Name a combination of Lepturus and Oropetium (related grass genera).

Habit, vegetative morphology. Wiry perennial; decumbent. Culms 30–50 cm high (slender); herbaceous; branched above. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 2.8–4 mm wide (5–7 cm long); flat, or folded, or rolled; without abaxial multicellular glands; without cross venation; persistent. Ligule a fringed membrane.

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

Inflorescence. Inflorescence a single spike (L. kuniense), or of spicate main branches (mostly paired, in L. marshallense); digitate, or non-digitate (when the racemes solitary). Primary inflorescence branches 1–3 (each with 10–16 spikelets). Rachides hollowed. Spikelets all partially embedded in the rachis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund to not secund (somewhat so, according to Morat); distichous; sessile; imbricate.

Female-fertile spikelets. Spikelets 4.5–7 mm long; adaxial; compressed laterally; disarticulating above the glumes, or falling with the glumes (?); not disarticulating between the florets (the rachilla not articulated). Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension with incomplete florets. Hairy callus present (beneath the L1).

Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; dorsiventral to the rachis; pointed (both or only the G2 acuminate); awned (the G2 sometimes shortly awn tipped), or awnless; non-carinate; very dissimilar (the G2 covering the spikelet, rigid, leathery, the G1 shorter and thinner - except in the terminal spikelet, where both glumes resemble a normal G2). Lower glume longer than half length of lowest lemma; 1 nerved. Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1 (sterile); merely underdeveloped; awnless.

Female-fertile florets 1 (L. kuniense), or 2 (L. marshallense). Lemmas less firm than the glumes (papery); not becoming indurated; incised (minutely so); 2 lobed; not deeply cleft; awned. Awns 1; median; from a sinus; non-geniculate; hairless (scabrid); much shorter than the body of the lemma to about as long as the body of the lemma (1.5–4.5 mm long); entered by one vein; persistent. Lemmas hairy (shortly pilose, at least apically); non-carinate; 3 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae (truncate-ciliate); thinner than the lemma; not indurated (hyaline); 2-nerved; 2-keeled. Palea keels wingless. Lodicules present (‘reduced’); 2. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2; red pigmented.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (and very abundant); costal and intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell, or several per cell (the interstomatals mostly with one large papilla, the long-cells often with a median row). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (hard to find amongst the abundant papillae); more or less spherical; ostensibly one-celled to clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 6 microns long. Microhair total length/width at septum 1.5. Microhair apical cell/total length ratio 0.6. Stomata common. Subsidiaries non-papillate; dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies confined to the central file(s) of the costal zones; predominantly saddle shaped (but many incompletely formed); not sharp-pointed.

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

C4; XyMS+. PCR sheath outlines conspicuously uneven (the minor bundles), or even (the primaries). PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (between all bundles); in simple fans (the median cells deeply penetrating), or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (the primaries with conspicuous I’s). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae. 2 species.

Distribution, phytogeography, ecology. New Caledonia, Marshall Islands, Cocos Islands.

Species of open habitats; presumably halophytic. Calcareous soil, in costal hinterland.

References, etc. Morphological/taxonomic: Morat 1981; Fosberg and Sachet 1982. Leaf anatomical: studied by us - L. marshallense Fosberg & Sachet.

Special comments. Possible intergeneric hybrids, involving Lepturus as one parent. Fruit data wanting.

Illustrations. • General morphology of Lepturopetium kuniense: Morat, Adansonia 20 (1981).

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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