Lepturella Stapf
Sometimes referred to Oropetium (O. aristatum (Stapf) Pilger, = sect. Lepturella)
Habit, vegetative morphology. Dwarf, cushion forming annual; caespitose. Culms 2–9 cm high; herbaceous; branched above. Culm nodes glabrous. Culm internodes hollow. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; about 2 mm wide (to 4 cm long); usually rolled; exhibiting multicellular glands abaxially (base of macrohairs). The abaxial leaf blade glands on the blade margins. Leaf blades without cross venation; disarticulating from the sheaths, or persistent; an unfringed membrane (laciniate, with only a few hairs), or a fringed membrane; truncate; about 0.2 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike (straight or curved, cylindrical, slender, short). Primary inflorescence branches 1 (i.e., solitary spikes). Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spikes; disarticulating; disarticulating at the joints (into segments each with one spikelet). ‘Articles’ non-linear; disarticulating transversely; glabrous. Spikelets solitary; not secund; distichous (the ranks opposite); sessile.
Female-fertile spikelets. Spikelets 2.5–3.5 mm long; adaxial; compressed laterally; falling with the glumes (and with the joint); with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present (short). Callus short.
Glumes two, or one per spikelet (the G1 reduced or missing, save in the terminal spikelet); very unequal (save in the terminal spikelets, which have equal glumes); exceeding the spikelets; (the upper) long relative to the adjacent lemmas; dorsiventral to the rachis; hairless; awned (G2 tapered into a long subule); carinate; very dissimilar (G1 a scarious scale or missing, G2 large, covering the floret, awned, rigid). Lower glume 0 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (membranous); not becoming indurated; incised; 2 lobed; not deeply cleft; awned. Awns 1; median; from a sinus; non-geniculate; hairless (scabrous); about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairless; without a germination flap; 3 nerved. Palea present (oblong); relatively long; entire; with apical setae (the keels shortly excurrent); membranous; not indurated; 2-nerved; 2-keeled. Palea keels wingless; glabrous. Lodicules present; 2; free; glabrous. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary glabrous. Stigmas 2; brown.
Fruit, embryo and seedling. Fruit compressed laterally. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 12 microns long. Microhair total length/width at septum 2. Microhair apical cell/total length ratio 0.5. Stomata common. Intercostal short-cells in cork/silica-cell pairs; silicified. Intercostal silica bodies imperfectly developed; tall-and-narrow. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped; not sharp-pointed (to squarish).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with the traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins without fibres.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 1 species (L. aristata); west tropical Africa. Mesophytic to xerophytic; species of open habitats; glycophytic.
Paleotropical. African. Sudano-Angolan and West African Rainforest. Somalo-Ethiopian and South Tropical African.
References, etc. Leaf anatomical: Metcalfe 1960; Van den Borre 1994.
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).