Derivation
Acrachne Wright & Arn. ex Chiov., Annuario Reale Ist. Bot. Roma 8: 361 (1907); from the Greek akra (the terminal point) and achne (a scale), referring to the fine-pointed glumes and lemmas.

racemosa- from the Latin racemus (stalk of a cluster of grapes) and -osa (abundance). The spikelets are borne in racemes or contracted panicles.

Published in
Bull. Tokyo Sci. Mus.18: 1 (1947).

Common synonyms
Acrachne verticillata (Roxb.) Chiov.

Habit
Annual, tufted. Basal leaf sheaths glabrous. Young shoots intravaginal. Culms geniculately ascending or decumbent, 15–100 cm tall, 1–3 mm diam., 2–6-noded. Lateral branches sparsely branched. Leaves cauline. Leaf-sheaths as wide as blade at the collar. Ligule a fringed membrane, 0.5–1.3 mm long. Leaf-blades flat, 13–75 cm long, 3–12 mm wide. Leaf-blade surface smooth, glabrous or pilose. Leaf-blade margins cartilaginous. Leaf-blade apex attenuate, filiform.

Inflorescence
Inflorescence subdigitate, a panicle of racemes, with racemose branches. Racemes 2–25, in several whorls, unilateral, 1.5–10 cm long. Central inflorescence axis 0–15 cm long. Rhachis angular, terminating in a sterile spikelet. Spikelet packing broadside to rhachis, regular.

Spikelets
Spikelets appressed, solitary. Apical sterile spikelets rudimentary, 1 in number. Fertile spikelets many flowered, comprising 6–25 fertile florets, with diminished florets at the apex, oblong, laterally compressed, 5–13 mm long, 2.5–3 mm wide, breaking up at maturity. Spikelets rhachilla persistent. Spikelets retaining paleas, tough throughout or fragile above, with the distal florets falling as a whole. Rhachilla internodes 0.1 mm long, eventually visible between lemmas.

Glumes
Glumes deciduous, similar. Lower glume linear or lanceolate or elliptic or oblong, 1.2–2.9 mm long, 50–80% length of upper glume, membranous or cartilaginous, 1-keeled, 1-nerved. Lower glume lateral nerves absent. Lower glume apex acuminate, mucronate. Upper glume ovate, 1.5–3 mm long, 50–70% of length of adjacent fertile lemma, membranous, 1-keeled, 1-nerved, midnerve scabrous. Upper glume lateral nerves absent. Upper glume apex entire, acuminate, mucronate.

Florets
Fertile florets recurved at tip. Fertile lemma lanceolate or elliptic or oblong or ovate, laterally compressed, ovate in profile, 2–3 mm long, membranous or cartilaginous, yellow to mid-green, 3-nerved. Lemma midnerve scaberulous. Lemma lateral nerves excurrent. Lemma surface glabrous. Lemma apex entire, acute, 1-awned. Median (principal) awn 0.3–0.9 mm long overall. Palea lanceolate or ovate, bowed outwards, 80% of length of lemma, 2-nerved. Palea keels scabrous. Palea apex dentate, 2-fid, acute. Apical sterile florets resembling fertile though underdeveloped. Lodicules 2, cuneate, fleshy. Anthers 3, 0.4 mm long. Stigmas 2, protandrous, laterally exserted. Grain with free soft pericarp, ellipsoid or oblong, terete, biconvex, estipitate, grooved, 0.8–1.1 mm long, rugose, apex unappendaged. Embryo 40% of length of grain. Hilum punctiform. Endosperm farinose.

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

Australian Distribution:
Western Australia, Northern Territory, Queensland.

Western Australia: Fortescue, Austin. Northern Territory: Darwin & Gulf, Victoria River, Barkly Tableland. Queensland: Burke, North Kennedy, South Kennedy, Leichhardt.

Classification. (GPWG 2001):
Chloridoideae: Cynodonteae

Notes
Recorded from the Pilbara and Kimberley Regions of W.A., the Darwin area and Barkly Tableland of the N.T., and central eastern Qld; pan-tropical. Occurs in brown, sandy loam over loamy clay on coastal flats in association with low, deciduous, vine thickets in the Kimberley Region of W.A.; otherwise in monsoonal areas usually along creeklines on sandy or skeletal soils, with Eucalyptus, Acacia or Atalaya species

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