Triraphis R.Br.
From the Greek treis (three) and raphis (a needle), referring to the three-awned lemmas.
Habit, vegetative morphology. Annual, or perennial; caespitose (mostly small xeromorphs). Culms (1–)4–140 cm high; herbaceous. Culm nodes glabrous. Culm internodes solid. Leaves mostly basal; non-auriculate. Leaf blades narrow; setaceous, or not setaceous; flat, or rolled (or junciform); without abaxial multicellular glands; without cross venation; persistent; a fringed membrane, or a fringe of hairs.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open, or contracted (rarely spiciform); when contracted, spicate to more or less irregular; with capillary branchlets, or without capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present.
Glumes two; relatively large; very unequal (rarely), or more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed (often bidentate); awned (or mucronate, from the sinus), or awnless; carinate; similar (narrow, persistent). 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 merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 3–10. Lemmas not becoming indurated (membranous); incised; 3 lobed, or 4 lobed (when the central lobe is bidentate); deeply cleft (on either side of the central lobe); awned. Awns 3; median and lateral (the lateral lobes setiform-awned or mucronate); the median similar in form to the laterals; from a sinus (of the central lobe); non-geniculate (setiform). The lateral awns shorter than the median. Lemmas hairy (villous on the lateral nerves); non-carinate (3-keeled), or carinate (when the lateral keels are near the margins); 3 nerved. Palea present; shorter than the lemma; apically notched, or deeply bifid; not indurated (hyaline); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy, or membranous; glabrous. Stamens 3. Anthers not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; linear; trigonous. Hilum short. Pericarp fused. Embryo large; waisted. Endosperm containing compound starch grains. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.
First seedling leaf with a well-developed lamina. The lamina broad (fairly); curved.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhairs without ‘partitioning membranes’ (in T. mollis); (40–)50–72(–75) microns long; (6–)6.6–7.5(–8.4) microns wide at the septum. Microhair total length/width at septum 6.8–11. Microhair apical cells (27–)30–42(–46) microns long. Microhair apical cell/total length ratio 0.44–0.63. Stomata common; (24–)25–31.5(–36) microns long. Subsidiaries parallel-sided and dome-shaped, or dome-shaped and triangular, or parallel-sided, dome-shaped, and triangular; including both triangular and parallel-sided forms on the same leaf. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal zones with short-cells. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’; cross shaped to butterfly shaped, or dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NAD–ME (T. mollis, although exhibiting ‘PCK-like’ leaf blade anatomy); XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions present. Maximum number of extension cells 3. PCR cells with a suberised lamella. PCR cell chloroplasts ovoid; with well developed grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size, or with the ribs very irregular in sizes. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans (in T. pumilio, according to Metcalfe 1960). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaf blade chlorophyll a:b ratio 4–4.01.
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 7 species; tropical and southern Africa, Australia. Mesophytic to xerophytic; species of open habitats; glycophytic. Savanna, in sandy or rocky soil.
Paleotropical and Australian. African. Saharo-Sindian, Sudano-Angolan, and Namib-Karoo. North and East Australian and Central Australian. South Tropical African and Kalaharian. Tropical North and East Australian and Temperate and South-Eastern Australian.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • Inflorescence, spikelet. • General aspect. • Inflorescence. Triraphis mollis. • Spikelet. • Spikelet (without glumes). • Lemma tip. • 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).
