Vacoparis macrospermum (E.D.Garber) Spangler. Austral. Syst. Bot. 16(3): 297 . (2003).
Classification. (GPWG 2001) : Subfamily Panicoideae. Andropogoneae.
Basionym and/or Replacement Name: Sorghum macrospermum E.D. Garber, Univ. Calif. Publ. Bot. 23(6): 323 (1950).
Type of Basionym or Protologue Information: HT: Anonymous s.n., Australia: Northern Territory: Darwin and Gulf District; UC-753385, specimen cultivated in 1948 from seed collected by W. Hartley "near Darwin" in 1947 (UC (photo, CANB)).
Key references (books and floras):  D.Sharp & B.K.Simon, AusGrass, Grasses of Australia.
Habit. Annual. Culms erect, stature robust to moderate, 180–380 cm tall, 5–10 mm diam. Mid-culm nodes glabrous or pubescent. Leaves cauline. Ligule a fringed membrane, a ciliolate membrane, 2.6–5 mm long. Leaf-blades 30–60 cm long, 15–30 mm wide. Leaf-blade surface glabrous or indumented.
Inflorescence. Inflorescence compound, a panicle of rames. Panicle ovate, effuse, 15–35 cm long. Rhachis fragile at the nodes.
Spikelets. Spikelets sessile, 1 in the cluster. Companion spikelets pedicelled, 1 in the cluster. Basal sterile spikelets absent or well-developed, 0–4 in number. Companion spikelets represented by single glumes or rudimentary, comprising 2 subequal glumes without lemmas, 6.5–13.5 mm long. Companion spikelet glumes muticous. Fertile spikelets 2-flowered, the lower floret barren (rarely male), the upper fertile, comprising 1 basal sterile florets, comprising 1 fertile floret(s), without rachilla extension, lanceolate, dorsally compressed, 10–11 mm long.
Glumes. Glumes dissimilar, firmer than fertile lemma, shiny. Lower glume ovate, coriaceous, much thinner above, without keels, 15–20 -nerved. Lower glume surface glabrous. Upper glume ovate, coriaceous, without keels, winged on margins, 7 -nerved. Upper glume surface scabrous, indumented. Florets. Basal sterile florets 1, barren, without significant palea. Lemma of lower sterile floret 80 % of length of spikelet, hyaline, 2 -nerved.
Fertile lemma 3.5–4 mm long, 1 -nerved. Lemma apex dentate, awned, 1 -awned. Median (principal) awn from a sinus, 30–52 mm long overall, with a twisted column. Palea absent. Lodicules present. Anthers 3. Grain 5.2–6.3 mm long.
Continental Distribution: Australasia.
Australian Distribution: Northern Territory.
Northern Territory: Darwin & Gulf.
Notes. Found in a small area of limestone outcrops north-west of Katherine, N.T. Flowers Feb.--Apr