Vacoparis Austr.Syst.Bot. (in press).
Derivation:. From Latin vaco (empty) and paris (companion), referring to the greatly reduced pedicelled spikelets.
Taxonomic revisions, nomenclatural references:. R.E.Spangler, Aust. Syst. Bot. (in press.).
Key references (keys and floras):. E.E.Henty, Manual Grasses New Guinea 173, 176–177 (1969) as Sorghum; M.Lazarides, Tropical Grasses S.E. Asia 72–73 (1980) as Sorghum; J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 378–381(1983) as Sorghum; B.K.Simon, Key to Australian Grasses 155–159 (1993) as Sorghum; D.Sharp and B.K.Simon, AusGrass (2002).
Native. 2 species, from Northern Australia to scattered locations in Indonesia and the Philippines. 2 species in Australia, NT and Qld. Also New Guinea.
Habit. Annual, tufted. Leaf blades broad or narrow. Ligule an unfringed membrane or a fringed membrane.
Inflorescence. Inflorescence paniculate, an open panicle with branches ending in racemes of paired spikelets, open or contracted. Spikelet-bearing axes paniculate.
Spikelets. Spikelets dorsally compressed, 2 flowered, with 1 fertile floret, paired, sessile and pedicelled, in pedicelled/sessile combinations; with rachilla terminating in a floret; sessile spikelet with lower incomplete floret. Fertile spikelets elliptic or lanceolate, dorsally compressed, falling with glumes.
Glumes. Glumes more or less equal, long relative to adjacent lemmas, awnless, dissimilar. Lower glume convex on back to flattened on back, relatively smooth, 11–17 nerved. Upper glume 7–9 nerved.
Florets. Lower incomplete floret(s) sterile. Lemmas awnless, similar in texture to fertile lemmas, not becoming indurated. Fertile florets 1. Lemmas not becoming indurated, incised, awned, glabrous. Awns 1, from a sinus, geniculate, hairless, much longer than body of lemma. Callus blunt. Stamens 3. Grain small or medium sized. Pedicels free of rachis. Pedicelled spikelets present, similar in shape to sessile spikelet, sterile, with glumes (only).
Kranz Anatomy. C4.
2n = 40, 4 ploid.
Habitat. Mesophytic. Species of open habitats.
Classification. Panicoideae; Andropogoneae.
Notes. A recent split from Sorghum (Spangler, in press).
Types Species. V. laxiflorum (Bailey) Spangler.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Endemic.