Ophiuros Fruct. 3: 3 (1805).
Derivation:. From Greek ophis (serpent) and oura (tail), alluding to the smooth spikes with the scale-like appressed lower glumes of the spikelets.
Key references (keys and floras):. G.Bentham, Flora Australiensis 7: 512 (1878); C.A.Gardner, Flora of Western Australia 1 Gramineae 310–312 (1952); M.Lazarides, Tropical Grasses S.E. Asia 60–61 (1980); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 314–315 (1983); B.K.Simon, Flora of the Kimberley Region 1192 (1992); B.K.Simon, Key to Australian Grasses 134 (1993); D.Sharp and B.K.Simon, AusGrass (2002).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (640).
Native. 4 species, from 1 in northeast tropical Africa, 6 in the Indomalayan region, Australia. 1 species in Australia, WA, NT, and Qld. Also Malesia.
Habit. Annual or perennial, tufted (forming tall clumps). Culms woody and persistent. Leaf blades broad or narrow. Ligule a fringed membrane.
Inflorescence. Inflorescence compound paniculate (with slender, cylindrical, distichous spikes, terminal on culm branches), a spatheathe panicle, spatheate, racemes paired or in clusters, not in tight heads, a compound pseudo-inflorescence. Spikelet-bearing axes spikelike (the spikelets sunk in hollows of the terete rachis), with heteromorphic spikelets (if the pedicellate members are perceived as spikelets), solitary or clustered (fascicled), disarticulating at joints. Internodes with a basal callus-knob, disarticulating transversely, glabrous.
Spikelets. Spikelets all partially embedded in rachis, dorsally compressed, 2 flowered, with 1 fertile floret, solitary (ostensibly solitary) or paired (acknowledging an adnate pedicel), sessile and pedicelled, in pedicelled/sessile combinations; sessile spikelet with lower incomplete floret. Fertile spikelets abaxial (with lower glume on side away from rachis), falling with glumes (and with the joint).
Glumes. Glumes more or less equal, long relative to adjacent lemmas, awnless, dissimilar (the lower thickly leathery or crustaceous, the upper thinly hyaline). Lower glume convex on back to flattened on back, lacunose with deep depressions or rugose (with a basal transverse groove), 5–7 nerved. Upper glume 3 nerved.
Florets. Lower incomplete floret(s) male, or sterile. Lemmas awnless, 0 nerved or 2 nerved, not becoming indurated. Fertile florets 1. Lemmas less firm than glumes (thinly membranous), not becoming indurated, muticous, 0 nerved or 2 nerved or 3 nerved, glabrous. Palea entire, 2 nerved. Lodicules 2. Stamens 3. Grain slightly compressed dorsiventrally. Embryo small (about 1/4 of the fruit length). Pedicels discernible, but fused with rachis. Pedicelled spikelets absent.
Kranz Anatomy. C4.
Habitat. Damp places in savanna.
Classification. Panicoideae; Andropogoneae.
Notes. A homogeneous genus, whose lower glume sculpturing suggests a relationship with Heteropholis (placed with Mnesithea by Veldkamp et al. (1986) (Clayton and Renvoize, 1986).
Types Species. O. corymbosus (L.f.) = O. exaltatus (L.) Kuntze
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Old World Tropics.