Eustachys* Nouv. Bull. Sci. Soc. Philom. Paris 2: 188 (1810).
Derivation:. From Greek eu (true) and stachys (spike), alluding to the fact that the infloresence branches are true spikes.
Taxonomic revisions, nomenclatural references:. M.Lazarides, Austr. J. Bot. Supp. Ser. 5: 23–24 (1972).
Key references (keys and floras):. M.Lazarides, Tropical Grasses S.E.Asia 160–161 (1980); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 246–247 (1983); J.P.Jessop, Flora of South Australia 4: 1954 (1986); B.K.Simon, Key to Australian Grasses 121 (1993); S.W.L.Jacobs and K.L.McClay, Flora of New South Wales 4: 520 (1993); D.Sharp and B.K.Simon, AusGrass (2002); K.Mallet (ed.), Flora of Australia 44B: Poaceae 3: 287 (2005)J.P.Jessop, Grasses of South Australia 384 (2006); S.W.L.Jacobs, R.D.B.Whalley & D.J.B.Wheeler, Grasses of New South Wales, 4th ed, 266(2008).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (392).
Naturalised. 10 species, from tropical America, West Indies, tropical and South Africa. 1 species in Australia, WA, SA, and Qld. Also Malesia.
Habit. Annual or perennial, tufted. Leaf blades broad or narrow. Ligule a fringe of hairs.
Inflorescence. Inflorescence of spicate main branches (pectinate spikes or spicate racemes), of digitate or subdigitate racemes or spikes, digitate.
Spikelets. Spikelets laterally compressed to subterete, 2 flowered, with 1 fertile floret, solitary (on one side of axis); with naked rachilla extension (but terminating in the incomplete floret). Fertile spikelets adaxial (with lower glume against rachis), disarticulating above glumes.
Glumes. Glumes relatively large (thinly membranous), unequal to more or less equal, shorter than adjacent lemmas, hairless, scabrous, blunt or incised, the upper awned (from below its apex), keeled, dissimilar (both membranous, but the upper glume broader and awned). Lower glume 1 nerved. Upper glume 1 nerved.
Florets. Fertile florets 1. Lemmas decidedly firmer than glumes (firmly membranous to leathery), not becoming indurated, dark brown in fruit, entire at apex or incised, muticous or mucronate or awned (shortly in E. distichophylla), 3 nerved, hairy (on margins and keel), 1 keeled. Palea entire (oblanceolate), thinner than lemma (scarious), 2 nerved. Palea keels winged (and ciliolate). Distal incomplete florets usually 2, underdeveloped (greatly reduced, or the lower male). Lodicules 2. Stamens 3. Grain small, ellipsoid, trigonous. Hilum short. Embryo large.
Kranz Anatomy. C4, biochemical type NAD-ME (E. distichophylla).
2n = 40, 4 ploid, commonly adventive.
Habitat. Mesophytic. Savanna, on a variety of soils. Species of open habitats.
Classification. Chloridoideae; Cynodonteae.
Notes. A close-knit group of species possessing a particular combination of characters, but otherwise barely separable from Chloris (Clayton and Renvoize, 1986).
Types Species. E. petraea (Sw.) E.Desv.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Naturalised.