Thaumastochloa Hooker's Icon. Pl. 34:Tab .3313–14:3 (1936).
Derivation:. From Greek thaumoastos (wonderful) and chloe (grass), presumably alluding to the decorative ornamentation of the spikelets.
Taxonomic revisions, nomenclatural references:. R. de Koning, M.S.M. Sosef and J.F.Veldkamp, Gard. Bull. Singapore 36:137–162 (1983); B.K. Simon, Austrobaileya 3: 90–92(1989).
Key references (keys and floras):. C.A.Gardner, Flora of Western Australia 1 Gramineae 309–310 (1952); E.E.Henty, Manual Grasses New Guinea 181 (1969); M.Lazarides, Tropical Grasses S.E. Asia 74–75 (1980); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 398–399 (1983); B.K.Simon, Flora of the Kimberley Region 1225–1227 (1992); B.K.Simon, Key to Australian Grasses 168 (1993); D.Sharp and B.K.Simon, AusGrass (2002).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (644).
Native. At least 9 species, from Northeast India, Southeast Asia to Taiwan, Philippines, Marianne & Caroline Is., Moluccas, Australia. 9 species in Australia, WA, NT, and Qld. Also New Guinea and Malesia.
Habit. Annual or perennial, rhizomatous. Leaf blades narrow. Ligule a fringed membrane to a fringe of hairs.
Inflorescence. Inflorescence a single raceme (usually compound, of single, pedunculate, cylindrical, dorsiventral racemes), a single raceme or spike, spatheate or espatheate (depending on interpretation), racemes single, not in tight heads, a compound pseudo-inflorescence or not a compound pseudo-inflorescence. Spikelet-bearing axes much reduced or spikelike (peduncled, slender, with one or few spikelets), with heteromorphic spikelets (the pedicelled spikelets greatly reduced), solitary, disarticulating at joints (the rachis fragile, but the lowest spikelet falling with the peduncle, which becomes stiff, curved and pointed to function in dispersal) or falling entire (the only spikelet falling with the specialised peduncle). Internodes with a basal callus-knob, disarticulating transversely to disarticulating obliquely.
Spikelets. Spikelets all partially embedded in rachis, dorsally compressed, 2 flowered, with 1 fertile floret, unaccompanied by bractiform involucres, not associated with setiform vestigial branches, paired (if the very reduced pedicelled spikelet is interpreted as such), sessile and pedicelled (the pedicelled member vestigial), in pedicelled/sessile combinations; with rachilla terminating in a floret; sessile spikelet with lower incomplete floret. Fertile spikelets falling with glumes (and with the joint).
Glumes. Glumes relatively large, more or less equal, long relative to adjacent lemmas, awnless, dissimilar (the lower indurated and sometimes rugulose, the upper hyaline and cymbiform). Lower glume two-keeled (wingless), convex on back to concave on back, transversely rugose or relatively smooth, 5–9 nerved. Upper glume 3–5 nerved.
Florets. Lower incomplete floret(s) sterile. Lemmas awnless, 2 nerved (towards the margins), more or less equalling fertile lemmas to exceeding fertile lemmas, similar in texture to fertile lemmas to decidedly firmer than fertile lemmas (hyaline). Fertile florets 1. Lemmas less firm than glumes (hyaline), not becoming indurated, entire at apex, blunt, muticous, 0–3 nerved, glabrous. Palea 1 nerved or 2 nerved or nerveless. Lodicules 2. Stamens 3. Grain compressed dorsiventrally. Hilum short. Embryo large. Pedicels discernible, but fused with rachis.
Kranz Anatomy. C4.
Classification. Panicoideae; Andropogoneae.
Notes. A specialised genus with a modified deciduous peduncle which assists in dispersal. The genus is probably derived from Heteropholis (Mnesithea in this key) (Clayton and Renvoize, 1986).
Types Species. T. pubescens (Domin) C.E.Hubb.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Indo-Malayan.