KEY TO THE SPECIES

1Stems smooth even at the top. Glumes ovate, 3-3¾ mm long. Flowers 3-3½ mm long. Nut broadly obovoid, abruptly acuminate at the apex
Thoracostachyum sumatranum
1'Stems more or less scabrous at the top. Glumes broadly ovate, 2-2¼ mm long. Flowers 1¾-2 mm long. Nut ellipsoid, slightly acuminate, with 3 longitudinal grooves in the conical beak
Thoracostachyum bancanum