Derivation
Tetrarrhena R.Br., Prodr. 209 (1810); from the Greek tetra (four) and arrhen (male). The flowers have four stamens.

laevis- Latin for smooth. Lacking hairs or roughness, usually of leaf-blades or lemmas.

Published in
Prodr. 210 (1810).

Common synonyms
Ehrharta laevis (R.Br.) Spreng.

Habit
Perennial, tufted. Rhizomes short. Stolons absent or present. Young shoots extravaginal. Culms erect or clambering, 25–70 cm tall, wiry. Leaf-sheath auricles absent. Ligule an eciliate or a fringed membrane, 0.1–0.3 mm long, membranous. Leaf-blades flat, 6–20 cm long, 2–8 mm wide. Leaf-blade surface scabrous. Monoecious, with male and female spikelets in the same inflorescence.

Inflorescence
Inflorescence solid, a raceme or a panicle. Panicle open, linear, 2.4–9 cm long. Primary panicle branches indistinct the panicle almost racemose. Rhachis scabrous on surface.

Spikelets
Spikelets solitary. Fertile spikelets 1-flowered, comprising 1 fertile floret, without rhachilla extension, oblong or ovate, laterally compressed, 7–8 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret.

Glumes
Glumes two, persistent, similar, thinner than fertile lemma. Lower glume oblong, 3–4.5 mm long, 75% length of upper glume, chartaceous, 5–9-nerved. Lower glume apex acute. Upper glume oblong, 3.4–4.8 mm long, 66% of length of spikelet, chartaceous, 5–7-nerved. Upper glume apex acute.

Florets
Basal sterile florets 2 or more, similar, without significant palea, attached to and deciduous with the fertile. Lemma of lower sterile floret oblong or ovate, without auricles, 6 mm long, 100% of length of spikelet, cartilaginous, 1-keeled, 5-nerved, distinctly nerved, smooth, glabrous or puberulous, with hooked hairs, obtuse or acute, muticous. Lemma of upper sterile floret oblong or ovate, basally simple, 4.7–6.7 mm long, 100% of length of lower sterile floret, cartilaginous, smooth, glabrous, obtuse or acute, muticous. Fertile lemma oblong, 4.5–6 mm long, coriaceous, 9-nerved. Lemma surface glabrous. Lemma apex obtuse. Palea 3.5 mm long, 1-nerved, 1-keeled. Lodicules 2, membranous, smooth, entire. Anthers 4–6. Male spikelets distinct from female, hairy. Male spikelet glumes 2, triangular or ovate, 1.1–1.8 mm long, 1–3-nerved, awned, with 0.4 mm long awn. Male spikelet lemma awned.

Continental Distribution:
Australasia.

Australian Distribution:
Western Australia: Drummond, Dale, Menzies, Warren, Eyre.

Classification. (GPWG 2001):
Ehrhartoideae: Ehrharteae

Notes
Endemic; restricted to W.A. Recorded from organic sandy loam soils or on granite in open eucalypt forest or in scrub. Flowers Sept.–Jan.