Whiteochloa Proc. Roy. Soc. Queensland 62: 111 (1952).
Derivation:. Named for Cyril Tenison White, Queensland Government botanist 1917–1950.
Taxonomic revisions, nomenclatural references:. M.Lazarides, Brunonia 1: 69–93 (1978).
Key references (keys and floras):. M.Lazarides, Tropical Grasses S.E. Asia 146 (1980); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 434–435 (1983); R.D.Webster, Australian Paniceae 255–261 (1987); T.D.Macfarlane, Flora of the Kimberley Region 1243–1244 (1992); B.K.Simon, Key to Australian Grasses 175–176 (1993); D.Sharp and B.K.Simon, AusGrass (2002).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (492).
Native. 6 species, from Australia and Moluccas. 6 species in Australia, WA, NT, and Qld.
Habit. Annual (or short-lived perennials), tufted to decumbent. Leaf blades narrow. Ligule a fringed membrane.
Inflorescence. Inflorescence paniculate, an open panicle with branches ending in single spikelets, open (the branches solitary, usually distant).
Spikelets. Spikelets 2 flowered, with 1 fertile floret, solitary or paired, pedicelled. Fertile spikelets with lower incomplete floret(s), oblong or elliptic or obovate, slightly laterally compressed or subterete, falling with glumes, with distinctly elongated rachilla internodes between florets. Upper floret borne on a swollen stipe (shortly so).
Glumes. Glumes unequal, (the upper) long relative to adjacent lemmas, hairy (upper glume hispid or ciliate on the nerves, with tubercle-based hairs) or hairless, awnless (sometimes mucronate), dissimilar (membranous, the lower glume. broadly ovate and enclosing the base of the spikelet, the upper glume larger, cymbiform, acuminate with a hardened apex). Lower glume 3–5 nerved. Upper glume 5–7 nerved (the nerves prominent).
Florets. Lower incomplete floret(s) male. Lemmas awnless, 5 nerved, exceeding fertile lemmas (with dorsal groove or depression), less firm than fertile lemmas to similar in texture to fertile lemmas (membranous to leathery), becoming indurated or not becoming indurated. Fertile florets 1. Lemmas decidedly firmer than glumes, faintly but distictly rugose, becoming indurated (crustaceous), yellow in fruit, entire at apex, pointed (acute or acuminate), mucronate (with a slightly curved apiculum), 5 nerved, hairy (apically puberulous) or glabrous (glabrous), having flat margins not tucked into palea. Palea relatively long, entire, indurated (with indurated flaps), 2 nerved. Stamens 3. Grain small, compressed dorsiventrally. Hilum short. Embryo large.
Kranz Anatomy. C4.
Habitat. Sandy alluvial soils in savanna. Species of open habitats.
Classification. Panicoideae; Paniceae.
Notes. A variable genus difficult to distinguish from Panicum as the characteristic upper rhachilla internode requires careful dissection (Clayton and Renvoize, 1986). Whiteochloa has an interesting combination of characters and its affinities within the tribe are unclear. The lateral compression of the spikelets and stipitate upper floret suggests affinity with Ichnanthus, Yakirra, or Arthragrostis. The rugose upper floret and spikelet bearing branches terminating in a spikelet suggests affinity with Eriochloa or Urochloa. However Whiteochloa is C4 subtype NADP-ME, whereas Eriochloa and Urochloa are C4 subtype PCK (Webster, 1987).
Types Species. W. semitonsa (F.Muell.) C.E.Hubb.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Endemic.