Plants annual or perennial; cespitose, sometimes stoloniferous, occasionally with rhizomes. Culms 2-60 cm. Sheaths open, throats glabrous or long-ciliate; ligules of hairs, or membranous and ciliate, or ciliolate; blades flat or rolled, glabrous or villous. Inflorescences terminal, sometimes also axillary, panicles, spikes, or racemes. Spikelets with 2-5(10) florets, distal florets reduced; disarticulation above the glumes and between the florets. Glumes exceeding or exceeded by the florets, herbaceous, 3-5-veined, glabrous or scabridulous, sometimes with stiff, papillose-based hairs, glume apices acute or acuminate; calluses glabrous; lemmas herbaceous, with acute or clavate hairs in marginal rows or variously scattered, lemma apices unlobed, acute to long-acuminate; paleas sometimes with tufts of hairs on the margins; lodicules 2, obtriangular, glabrous or with bristles, 1-3-veined, lodicule apices at least as thick as the base; anthers 3, 0.3-3.1 mm. Caryopses 0.7-2.2 mm long, 0.4-1.1 mm wide; pericarp poorly separable, dull, smooth or rugulose, glabrous; embryos 1/3-1/2 as long as the caryopses; hila punctiform. x = 6. Desvaux did not explain the etymology of Tribolium. It may be derived from the Greek trilobos, a name of various prickly plants (Quattrocchi 1999) or the Latin tria, three, and bolus, a fiery meteor in the form of an arrow, referring to the appearance of the mature spikelets with their three florets and coarsely hairy glumes, which, like the lemmas, may be awned or acuminate (Clifford 1996).

Tribolium is a southern African genus of 10 species. It is unusual in the tribe in having unlobed lemmas, but has the haustorial synergids, bilobed or bi-awned prophylls, and stalked ovaries characteristic of the tribe. Linder and Davidse (1997) suggested that its closest relatives are probably Schismus, Karroochloa, and Rytidosperma.

1.   Tribolium obliterum (Hemsley) Renvoize

Plants perennial; usually cespitose, sometimes stoloniferous, stolons to 30 cm. Culms 12-40 cm, decumbent or erect, branching intravaginal. Sheaths mostly glabrous, ciliate distally; ligules about 0.2 mm, membranous, ciliolate; blades 1-8 cm long, 0.5-1 mm wide. Inflorescences terminal, panicles, 1-5 cm long, 5-15 mm wide, obovate or cylindrical, with 10-40 spikelets; branches scabridulous. Spikelets 3.5-4.5 mm, with 5-10 florets. Glumes 2.5-3.5 mm, longer than the basal lemmas but exceeded by the distal florets, 5-veined, glabrous or scabridulous over the veins, acute; lemmas 2-3.5 mm, with submarginal tufts of hairs in the lower 1/2, hairs acute, 0.2-0.3 mm, lemma apices acute to acuminate; paleas 1.5-2 mm, glabrous between the keels, sometimes with tufts of hairs on the margins; anthers 0.3-0.5 mm, pale yellow. Caryopses obovate, 0.7-1 mm long, 0.5-0.7 mm wide, plano-convex to concavo-convex, pale brown, smooth; embryos 0.4-0.5 mm; hila 0.1 mm. 2n = 24, 36.

Tribolium obliterum is native to Cape Province, South Africa, where it usually grows in gravelly, well-drained soils at elevations below 600 m. It has been introduced into Australia and St. Helena and was recently discovered in a roadside ditch near Fort Ord, Monterey County, California. It appears to be naturalized there.