Derivation
Brachyachne (Benth.) Stapf, in D.Prain (ed.), Fl. Trop. Africa 9: 20 (1917) in clavis; from the Greek brachys (short) and achne (scale, chaff), alluding to lemmas shorter than glumes.

prostrata- from the Latin prosterno (throw to the ground). Culms creeping or wiry so as to fall on the ground.

Published in
Hooker's Icon. Pl. 34: t. 3362 (1938).

Habit
Annual, mat forming. Stolons absent. Basal leaf sheaths glabrous or pilose. Culms prostrate, 5–10 cm tall, rooting from lower nodes. Lateral branches branched. Leaf-sheaths 0.5–1.5 cm long, striately nerved. Ligule an eciliate or a fringed membrane, 0.5 mm long. Leaf-blades lanceolate, 1–11 cm long, 0.5–1.5 mm wide, rigid. Leaf-blade surface glabrous or pubescent. Leaf-blade margins cartilaginous, scaberulous. Leaf-blade apex obtuse or abruptly acute or acute.

Inflorescence
Inflorescence digitate, with spicate branches, subtended by a spatheole, embraced at base by subtending leaf or enclosed. Spatheole lanceolate, 0.5–2 cm long. Spikes 3–4, unilateral, 0.4–1.1 cm long. Spikes 1.3–1.8 mm wide. Rhachis flattened, scaberulous on margins. Spikelet packing broadside to rhachis, imbricate, regular, 2-rowed.

Spikelets
Spikelets appressed, solitary. Fertile spikelets 1-flowered, comprising 1 fertile floret, with a barren rhachilla extension, lanceolate or elliptic or oblong, laterally compressed, compressed strongly, obtuse, 3–3.5 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Floret callus pilose.

Glumes
Glumes deciduous, dissimilar, with lower wider than upper, firmer than fertile lemma, parallel to lemmas. Lower glume elliptic, 3–3.5 mm long, 100% length of upper glume, membranous, 1-keeled, 1-nerved, midnerve scaberulous. Lower glume lateral nerves absent. Lower glume apex obtuse or acute. Upper glume elliptic or oblong, 3–3.5 mm long, 130–140% of length of adjacent fertile lemma, indurate, with membranous margins, 1-nerved, midnerve grooved on either side. Upper glume lateral nerves absent. Upper glume surface asperulous. Upper glume apex obtuse or acute.

Florets
Fertile lemma elliptic, laterally compressed, 2–2.5 mm long, membranous, 3-nerved. Lemma surface pubescent, with marginal hair tufts and with tufts of hair on midnerve, bearing 3 hair tufts in all. Lemma hairs 1 mm long. Lemma apex obtuse, muticous. Palea 100% of length of lemma, 2-nerved. Palea keels ciliate. Rhachilla extension 1 mm long. Anthers 3, 0.7–0.9 mm long. Grain obovoid, laterally compressed, 1.2–1.5 mm long. Embryo 50–75% of length of grain.

Continental Distribution:
Australasia.

Australian Distribution:
Western Australia, Northern Territory, Queensland.

Western Australia: Keartland, Fortescue, Ashburton, Carnarvon, Austin. Northern Territory: Victoria River, Central Australia North, Central Australia South. Queensland: Gregory North.

Classification. (GPWG 2001):
Chloridoideae: Cynodonteae

Notes
Endemic; W.A., Qld. and western N.T., arid areas along the flanks of the Great Sandy, Gibson and Great Western Deserts, including the Pilbara region; occurs in arid areas on stony flats and plains, including gibber plains (hard red stony soil) and granite elevated 'breakaway' country, sometimes between tussock grasses or Acacia shrubs; usually infrequent.