Grass Genera of the World

L. Watson 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; a fringed membrane.

Reproductive organization. Plants bisexual, 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. 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. Spikelets without proximal incomplete florets.

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 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.

Taxonomy. Chloridoideae; main chloridoid assemblage.

Distribution, ecology, phytogeography. 2 species; New Caledonia, Marshall Islands, Cocos Islands. Species of open habitats; presumably halophytic. Calcareous soil, in costal hinterland.

Paleotropical and Neotropical. Polynesian and Neocaledonian. Polynesian. Caribbean.

References, etc. Morphological/taxonomic: Morat 1981; Fosberg and Sachet 1982. Leaf anatomical: this project.

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

Illustrations. • General morphology


Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).

Index