Tetrarrhena R.Br.
From the Greek tetra (four) and arrhen (male), alluding to four stamens.
Sometimes referred to Ehrharta
Habit, vegetative morphology. Perennial; stoloniferous and decumbent. Culms woody and persistent to herbaceous; scandent (often), or not scandent (wiry, often long and scrambling, ‘sometimes capable of entangling a horse’); branched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; flat (or concave), or rolled; not pseudopetiolate; cross veined (rarely), or without cross venation; persistent; an unfringed membrane to a fringed membrane; truncate; short. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted; a single raceme (spike-like, the axis flexuous); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; subsessile.
Female-fertile spikelets. Spikelets 4.8–7 mm long; compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; not pointed (truncate); awnless; similar (leathery to scarious). Lower glume 1 nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2; epaleate; sterile. The proximal lemmas awnless; faintly 7 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas (tough); not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (leathery); not becoming indurated; entire; blunt; awnless; hairless; carinate to non-carinate; 7 nerved. Palea present; relatively long, or conspicuous but relatively short; entire (acute); awnless, without apical setae; thinner than the lemma (membranous); not indurated; 1-nerved; one-keeled (laterally compressed). Lodicules present (large); 2; membranous; ciliate, or glabrous; toothed, or not toothed; relatively heavily vascularized (cf. Ehrharta). Stamens 4 (usually), or 2 (T. oreophila). Anthers 2–3 mm long; not penicillate. Ovary glabrous. Styles free to their bases.
Fruit, embryo and seedling. Fruit compressed laterally. Hilum short. Embryo small. Endosperm containing compound starch grains. Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode.
Seedling with a short mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 5 veined.
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; panicoid-type; (30–)34–60(–63) microns long; 4.5–5.1 microns wide at the septum (T. oreophila), or 9.6–18 microns wide at the septum. Microhair total length/width at septum 2.1–7.1, or 10 (in T. oreophila). Microhair apical cells (10.5–)12–35(–36) microns long. Microhair apical cell/total length ratio 0.31–0.71. Stomata absent or very rare; 22.5–45 microns long. Subsidiaries dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow, or rounded (or oval), or crescentic. Costal short-cells conspicuously in long rows. Costal silica bodies rounded, or ‘panicoid-type’; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. PBS cells without a suberised lamella. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma; without adaxial palisade; without arm cells; without fusoids. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section, or adaxially flat; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’, or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Taxonomy. Bambusoideae; Oryzodae; Ehrharteae.
Distribution, ecology, phytogeography. 5 species; Australia. Shade species.
Australian. North and East Australian and South-West Australian. Tropical North and East Australian and Temperate and South-Eastern Australian.
Rusts and smuts. Rusts — Puccinia.
References, etc. Morphological/taxonomic: Vickery 1975; Willemse 1982. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • General aspect, spikelet. • Abaxial epidermis of leaf blade. • Transverse section of leaf blade. Tetrarrhena juncea.
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).
