Digitaria Hist. Stirp. Helv. 2: 244 (1768).
Derivation:. From Latin digitus (finger), alluding to the digitate inflorescence.
Taxonomic revisions, nomenclatural references:. J.Th.Henrard, Monograph genus Digitaria (1950): R.D.Webster, Brunonia 6: 131–216 (1984).
Key references (keys and floras):. C.A.Gardner, Flora of Western Australia 1 Gramineae 224–230 (1952); J.W.Vickery, Flora of New South Wales, Gramineae 19: 83–104 (1961); E.E.Henty, Manual Grasses New Guinea 72–73, 76–77, 88 (1969); M.Lazarides, Tropical Grasses S.E. Asia 113–118 (1980); M.Lazarides, Flora of Central Australia 472–474 (1981); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 192–196 (1983); J.P.Jessop, Flora of South Australia 4: 1962–1965 (1986); R.D.Webster, Australian Paniceae 35–70 (1987); T.D.Macfarlane, Flora of the Kimberley Region 1147–1150 (1992); B.K.Simon, Key to Australian Grasses 100–103 (1993); S.W.L.Jacobs and S.M.Hastings, Flora of New South Wales 4: 455–462 (1993); N.G.Walsh, Flora Victoria 2: 606–610 (1994); D.I.Morris, Student's Flora of Tasmania 4B: 345–347 (1994); E.Edgar and H.E.Connor, Flora of New Zealand 5: 539–545 (2000); D.Sharp and B.K.Simon, AusGrass (2002); J.P.Jessop, Grasses of South Australia 437–444 (2006); S.W.L.Jacobs, R.D.B.Whalley & D.J.B.Wheeler, Grasses of New South Wales, 4th Ed, 211–222 (2008)
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (524).
Native and naturalised. 220 species, from mainly warm regions. 41 species in Australia, WA, NT, SA, Qld, NSW, Vic, and Tas. Also New Guinea, Malesia and New Zealand.
Habit. Annual or perennial, rhizomatous or stoloniferous or tufted or decumbent (sometimes sward forming). Leaf blades broad or narrow. Ligule usually an unfringed membrane.
Inflorescence. Inflorescence nearly always of spicate main branches (rarely with some secondary branchlets or a single raceme), a racemose panicle with spikelets all similar or of digitate or subdigitate racemes or spikes, open or contracted, digitate or subdigitate or non-digitate. Spikelet-bearing axes with spikelets in pairs, one sessile, the other pedicelled.
Spikelets. Spikelets dorsally compressed, 2 flowered, with 1 fertile floret, solitary or paired to in triplets (usually in groups of 2–3), pedicelled. Fertile spikelets with lower incomplete floret(s), elliptic or lanceolate or ovate or obovate, abaxial (with lower glume on side away from rachis), dorsally compressed, falling with glumes.
Glumes. Glumes one per spikelet or two, unequal (the lower tiny or suppressed), shorter than adjacent lemmas or long relative to adjacent lemmas (i.e., the upper, sometimes), pointed or blunt, awnless, non-keeled, dissimilar. Lower glume when present, much shorter than half length of lowest lemma, 0–1 nerved or 3 nerved (at the base). Upper glume gibbous or not, 3–7 nerved (rarely nerveless).
Florets. Lower incomplete floret(s) sterile. Lemmas usually as long as the spikelet, usually hairy, the hairs between the first and second lateral nerves and along the margins, awnless, 3–7(–11) nerved, exceeded by fertile lemmas to exceeding fertile lemmas, less firm than fertile lemmas, not becoming indurated. Fertile florets 1. Lemmas similar in texture to glumes to less firm than glumes, smooth to striate, yellow in fruit or brown in fruit or black in fruit, entire at apex, pointed (mostly subacute to acuminate), muticous (but often apiculate), with a clear germination flap, obscurely 1–3 nerved, glabrous (no more than minutely striate-papillate), having flat margins not tucked into palea, not keeled or 1 keeled. Palea relatively long (about equalling the lemma), entire, textured like lemma, 2 nerved. Lodicules 2. Stamens 3. Grain small, compressed dorsiventrally. Hilum short. Embryo large.
Kranz Anatomy. C4, biochemical type NADP-ME (D. sanguinalis).
2n = 18, 30, 36, 45, 54, 60, 70, 72, and 76 or 108, commonly adventive.
Habitat. Mesophytic, xerophytic. Diverse habitats, including weedy ground and sandy beaches. Mostly species of open habitats.
Classification. Panicoideae; Paniceae.
Notes. The genus is extremely variable in inflorescence, relative length of spikelet scales, and spikelet indumentum; the latter display different combinations of appressed pubescence, glassy bristles and marginal cilia within the same species or even between the two members of a spikelet pair. Despite this the overall facies of the spikelet is surprisingly uniform, and the genus is seldom difficult to recognise (Clayton and Renvoize, 1986).
Types Species. D. sanguinalis (L.) Scop.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Gondwanan.
