Sporobolus australasicus Domin. Repert. Spec. Nov. Regni Veg. 9: 553 (1911).
Classification. (GPWG 2001) : Subfamily Chloridoideae. Cynodonteae.
Type of Basionym or Protologue Information: LT: F. Mueller s.n., Australia: Northern Territory: Upper Victoria River (K (photo, BRI)). LT designated by Simon, Fl. Austral. 44B: 459 (2005). LT: Domin s.n., Mar 1910, Australia: Queensland: Hyghendon [Hyghenden], Rolling Downs (PR; IT: K, NSW). LT designated by Baaijens & Veldkamp, Blumea 35: 451 (1991), but this is not original material and, therefore, is ineligible for lectotypification. See Simon, Fl. Austral. 44B 459 (2005).
Key references (books and floras):  C.A.Gardner, Flora of Western Australia 1 Gramineae (162),  M.Lazarides in J.Jessop (ed)., Flora of Central Australia (467),  D.Sharp & B.K.Simon, AusGrass, Grasses of Australia,  J.Jessop, G.R.M.Dashorst, F.M.James, Grasses of South Australia (397).
Illustrations:  C.A.Gardner, Flora of Western Australia 1 Gramineae (161, Pl. 48),  J.Jessop, G.R.M.Dashorst, F.M.James, Grasses of South Australia (397, fig. 329).
Habit. Annual or ephemeral. Culms erect or geniculately ascending, 20–40 cm tall, 3–5 -noded. Mid-culm nodes glabrous. Lateral branches simple or branched. Leaves mostly basal. Leaf-sheaths glabrous on surface. Ligule a fringe of hairs, 0.8 mm long. Leaf-blades linear, flat, 3–6 cm long, 4–8 mm wide. Leaf-blade surface indumented.
Inflorescence. Inflorescence compound, a panicle. Panicle oblong or pyramidal, 5–13 cm long, 4–6 cm wide.
Spikelets. Spikelets pedicelled. Fertile spikelets 1-flowered, comprising 1 fertile floret(s), without rachilla extension, orbicular, terete, 1–1.4 mm long.
Glumes. Lower glume ovate, membranous, much thinner on margins, without keels, 1 -nerved. Upper glume lanceolate or ovate, 1–1.4 mm long, membranous, without keels, 1 -nerved.
Florets. Fertile lemma 1–1.4 mm long, without keel, 1 -nerved. Palea 2 -nerved. Anthers 3. Grain 0.6–0.75 mm long.
Continental Distribution: Australasia.
Australian Distribution: Western Australia, Northern Territory, South Australia, Queensland.
Northern Territory: Darwin & Gulf, Victoria River, Barkly Tableland, Central Australia North. South Australia: Lake Eyre. Queensland: Burke, Cook, Gregory North, Leichhardt, Mitchell, North Kennedy, South Kennedy, Warrego, Port Curtis, Gregory South.
Notes. A number of specimens in the northern region of Western Australia (Lazarides 8485, Gardner 7199, Burbidge 1378, Burbidge 755, George 14760) are rather atypical. The grains are not globose but rather ovoid and flat, the spikelets are slightly larger and less convex than usual and the panicle branches sometimes naked in the lower section rather than spiculate almost to the base. However, these specimens otherwise match typical S. australasicus, with subcordate leaves having spinose margins peculiar to the species, the comparatively long ciliate ligules and the purple spikelets with the lower glume 1-nerved and half the length of the upper glume. Therefore no attempt has been made to separate them from S. australasicus.
Endemic; widely distributed in tropical and subtropical Australia. Collections tend to highlight the road systems. Flowers all year in response to rain.