Polytrias Engler and Prantl, Nat. Pfl.-Fam. II, 2: 24 (1887).
Derivation:. From Greek poly (many) and trias (in threes), alluding to the raceme of spikelets arranged in groups of three.
Key references (keys and floras):. E.E.Henty, Manual Grasses New Guinea 162–163 (1969); M.Lazarides, Tropical Grasses S.E. Asia 63–64 (1980); B.K.Simon, Key to Australian Grasses 152 (1993); D.Sharp and B.K.Simon, AusGrass (2002).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (574).
Native. 1 species, from Java to Australia. Qld. Also New Guinea.
Habit. Creeping, mat-forming perennial, stoloniferous. Leaf blades narrow. Ligule a fringed membrane (short).
Inflorescence. Inflorescence a single raceme, a single raceme or spike. Spikelet-bearing axes racemes (many-jointed), more or less with homomorphic spikelets (the pedicelled smaller, sometimes male-only), solitary, disarticulating at joints. Internodes disarticulating obliquely, densely long-hairy (the hairs brown).
Spikelets. Spikelets dorsally compressed, 2 flowered (lower floret suppressed), with 1 fertile floret, in triplets, sessile and pedicelled, in pedicelled/sessile combinations (two sessile, one pedicelled). Fertile spikelets falling with glumes (the pedicelled falling from its pedicel, the sessile with the internode and pedicel).
Glumes. Glumes more or less equal, long relative to adjacent lemmas, hairy, awnless, dissimilar (truncate, the lower glume cartilaginous and 2-keeled, the upper glume longer and naviculate). Lower glume two-keeled, flattened on back to concave on back, relatively smooth, 4 nerved (with no median). Upper glume 3 nerved.
Florets. Fertile florets 1. Lemmas less firm than glumes (thinly membranous), not becoming indurated, incised, deeply cleft (the lobes narrow, hairy), awned, 1 nerved, hairy (on the lobes). Awns 1, from a sinus, geniculate, much longer than body of lemma. Palea 2 nerved. Stamens 3. Hilum short. Embryo large. Pedicels free of rachis. Pedicelled spikelets present, similar in shape to sessile spikelet, bisexual or male.
Kranz Anatomy. C4.
Habitat. Waste land, roadsides. Species of open habitats.
Classification. Panicoideae; Andropogoneae.
Notes. A homogeneous genus, whose species are barely separable (Clayton and Renvoize, 1986).
Types Species. P. praemorsa (Steud.) Hack. = P. indica (Houtt.) Veldk.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Indo-Malayan.