Derivation
Oplismenus P.Beauv., Fl. Oware 2: 14 (1810); from the Greek hoplismenos (armed), alluding to the awns.

undulatifolius- from the Latin undulatus (wavy) and folium (leaf). The surface of the leaf-blade assumes the form of shallow waves.

Published in
Biblioth. Bot. 85: 329 (1915).

Habit
Perennial. Culms prostrate, 12–50 cm tall. Mid-culm nodes glabrous. Ligule a fringed membrane, 0.5–1 mm long. Collar hairy. Leaf-blades lanceolate or ovate, 1–10 cm long, 4–15 mm wide. Leaf-blade venation with obscure cross nerves. Leaf-blade surface scabrous, woolly.

Inflorescence
Inflorescence compound, a panicle of racemes. Racemes 5–11, cuneate, unilateral, 0.5–1 cm long, bearing 2–6 fertile spikelets on each (in a fascicle). Central inflorescence axis 2–10 cm long. Rhachis angular, glabrous or pilose on surface. Spikelet packing imbricate.

Spikelets
Spikelets solitary or in pairs, subequal or the lower smaller. Pedicels oblong. Fertile spikelets 2-flowered, comprising 1 fertile floret, lower floret sterile or male, upper fertile, without rhachilla extension, lanceolate, laterally compressed, 2.5–4 mm long, falling entire.

Glumes
Glumes similar or dissimilar, thinner than fertile lemma. Lower glume ovate, 1.7–2.7 mm long, equalling upper glume, 50–75% of length of spikelet, herbaceous, 1-keeled, 3–5-nerved. Lower glume surface glabrous or pubescent. Lower glume apex acute, awned. Lower glume awn 7–14 mm long, viscid. Upper glume ovate, 1.7–2.6 mm long, herbaceous, 1-keeled, 5–7-nerved. Upper glume surface glabrous or pubescent. Upper glume apex obtuse, muticous or awned. Upper glume awn 0–4 mm long.

Florets
Basal sterile floret 1, with palea or without significant palea. Lemma of lower sterile floret ovate, 2.7–3.8 mm long, 100% of length of spikelet, membranous, 1-keeled, 7–11-nerved, glabrous or pubescent, ciliate on margins, emarginate, mucronate or awned. Fertile lemma oblong, dorsally compressed, 2–3.6 mm long, coriaceous, glossy, 7-nerved. Lemma margins involute. Lemma apex acute, laterally pinched. Palea involute, coriaceous, without keels.

Continental Distribution:
Europe, Africa, Temperate Asia, Tropical Asia, Australasia.

Australian Distribution:
Queensland, New South Wales.

Queensland: Cook, North Kennedy, South Kennedy, Wide Bay, Moreton. New South Wales: North Coast.

Classification. (GPWG 2001):
Panicoideae: Paniceae

Notes
Native. Flowers Apr.–Aug. Diagnostic features of O. undulatifolius include the smooth awn and lowermost primary branches reduced to fascicles.