Tetrapogon Desf.
Including Codonachne Steud., Cryptochloris Benth., Lepidopironia A. Rich.
Habit, vegetative morphology. Annual, or perennial; stoloniferous, or caespitose. Culms 13–85 cm high; herbaceous. Culm nodes glabrous (pale or dark). Leaves not basally aggregated; non-auriculate. Sheath margins free. The sheaths keeled. Leaf blades linear (tapered); narrow; usually folded; without abaxial multicellular glands; without cross venation; a fringed membrane; very narrow.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous.
Inflorescence. Inflorescence a single spike, or of spicate main branches (comprising 1–3 upright racemes or spikes, of which 2 may be partly or completely fused along their backs); digitate, or subdigitate, or non-digitate. Primary inflorescence branches 1–3. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; secund (the rachis one-sided); biseriate; subsessile.
Female-fertile spikelets. Spikelets 2.5–12 mm long; cuneate; compressed laterally; disarticulating above the glumes (the glumes persistent); not disarticulating between the florets, or disarticulating between the florets (but under the fertile florets only). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present.
Glumes two; relatively large; more or less equal; long relative to the adjacent lemmas; hairless; glabrous; pointed (acute or acuminate); awned (awn-tipped), or awnless; carinate; similar (lanceolate, long-pointed, subhyaline). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1–4; awned.
Female-fertile florets 2–7. Lemmas decidedly firmer than the glumes (herbaceous, leathery, the margins hyaline); not becoming indurated; entire (truncate), or incised; when entire blunt; not deeply cleft; awned. Awns 1; median; dorsal; from near the top; non-geniculate; much longer than the body of the lemma. Lemmas hairy (on the back, the margins glabrous); carinate; 3–5 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated (membranous, sometimes hairy); 2-nerved; 2-keeled. Palea keels hairy (ciliate). Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 0.5–0.7 mm long; not penicillate. Ovary glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.5–3 mm long); ellipsoid; compressed laterally (in one species), or compressed dorsiventrally. Hilum short. Pericarp free. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae small, consisting of one oblique swelling per cell. Mid-intercostal long-cells rectangular; having markedly sinuous walls (coarsely so). Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 18–21 microns long. Microhair basal cells 15 microns long. Microhairs (6–)7.2–8.4 microns wide at the septum. Microhair total length/width at septum 2.1–3. Microhair apical cells (7.5–)9–10.5 microns long. Microhair apical cell/total length ratio 0.42–0.58. Stomata common; 13.5–15 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section to adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans (mostly, with deeply penetrating median cells), or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); forming ‘figures’ (in the primaries). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid. Chromosomes ‘small’.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 5–6 species; Mediterranean to India, tropical and South Africa. Helophytic to mesophytic; shade species, or species of open habitats; glycophytic. Savanna.
Holarctic and Paleotropical. Tethyan. African and Indomalesian. Macaronesian and Irano-Turanian. Saharo-Sindian, Sudano-Angolan, and Namib-Karoo. Indian. Sahelo-Sudanian, Somalo-Ethiopian, and South Tropical African.
Economic importance. Important native pasture species: T. tenellus (and other species potentially useful), in dry places.
References, etc. Morphological/taxonomic: Launert 1970. Leaf anatomical: this project.
Illustrations. • General aspect. • Abaxial epidermis of leaf blade. • Transverse section of leaf blade
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).
