Acrachne racemosa

Acrachne racemosa (B.Heyne ex Roem.
& Schult.) Ohwi. Bull. Tokyo Sci. Mus.18: 1 (1947). Classification. (GPWG 2001) : Subfamily Chloridoideae. Cynodonteae.

Basionym and/or Replacement Name:  Eleusine racemosa Heyne ex Roem. & Schult., Syst.2: 583 (1817).

Type of Basionym or Protologue Information: India orientali, D.B. Heyne s.n..

Recent synonyms: Acrachne verticillata (Roxb.) Chiov.

Key references (books and floras): [1878] G.Bentham, Flora Australiensis 7 (616, as Eleusine verticillata), [1952] C.A.Gardner, Flora of Western Australia 1 Gramineae (208 as Acrachne verticilllata), [1980] M.Lazarides, Tropical Grasses S.E.Asia (167), [1983] J.C.Tothill & J.B.Hacker, Grasses of Southern Queensland (79), [1992] J.R.Wheeler et al, Flora of the Kimberley Region (1120), [2002] D.Sharp & B.K.Simon, AusGrass, Grasses of Australia, [2005] K.Mallet (ed.), Flora of Australia 44B: Poaceae 3 (313).

[1952] C.A.Gardner, Flora of Western Australia 1 Gramineae (209, Pl.62 as A. verticillata), [1983] J.C.Tothill & J.B.Hacker, Grasses
of Southern Queensland
(78), [2002] D.Sharp & B.K.Simon, AusGrass, Grasses of Australiia, [2005] K.Mallet (ed.), Flora of Australia 44B: Poaceae 3 (Fig. 54A-C).

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

Habit. Annual. Culms geniculately ascending or decumbent, 15–100 cm tall, 1–3 mm diam., 2–6 -noded. Lateral branches sparsely branched. Leaves cauline. Ligule a fringed membrane, a ciliolate membrane or a ciliate membrane, 0.5–1.3 mm long. Leaf-blades flat, 13–75 cm long, 3–12 mm wide. Leaf-blade surface smooth, glabrous or indumented.

Inflorescence subdigitate, a panicle of racemes, with racemose branches. Racemes 2–25, 1.5–10 cm long. Central inflorescence axis 0–15 cm long.

Spikelets sessile. Apical sterile spikelets rudimentary. Fertile spikelets many flowered, with at least 2 fertile florets (6–25), comprising 6–25 fertile floret(s), with diminished florets at the apex, oblong, laterally compressed, 5–13 mm long.

Glumes. Glumes similar. Lower glume linear or lanceolate or elliptic or oblong, membranous or cartilaginous, keeled, 1-keeled, 1 -nerved. Lower glume apex mucronate. Upper glume ovate, 1.5–3 mm long, membranous, keeled, 1-keeled, 1 -nerved. Upper glume apex entire, mucronate.

Fertile lemma 2–3 mm long, keeled, 3 -nerved. Lemma surface glabrous. Lemma apex entire, awned, 1 -awned. Median (principal) awn 0.3–0.9 mm long overall. Palea 2 -nerved. Palea apex dentate. Lodicules present. Anthers 3. Grain 0.8–1.1 mm long.

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

Australian Distribution: Western Australia, Northern Territory, Queensland.

Western Australia: Gardner, Hall. Fortescue, Ashburton. Northern Territory: Victoria River. Queensland: Burke, Leichhardt, North Kennedy, South Kennedy.

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.

AVH 2011 

Inflorescence (scanned specimen) © Queensland Herbarium by Will Smith         Habit and spikelet (line drawing) © Gardner 1952   

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith