Ischaemum rugosum var. segetum (Trin.) Hack. in DC., Monogr. Phan. 6: 208. 1889. Hsu, Fl. Taiwan 5: 670. 1978.
Ischaemum segetum Trin., Mem. Acad. Sci. Petersb. Ser. 6, 2: 294. 1832.
Ischaemum tashiroi Honda, Bot. Mag. Tokyo 37: 365. 1923, 38: 50. 1924, Monogr. 365.1930.
Culms erect, up to 50 cm high, 3-7-noded, nodes bearded. Blade linear-lanceolate, 4-20 cm long, margins scabrous, usually soft hairy; ligule rounded, membranous, 2-4 mm long; sheath loose, margin ciliate, usually shorter than the internode. Racemes paired, 3-8 cm long; rachis and pedicel swollen, about 2/3 as long as the spikelet, ciliate. Spikelets paired, one pedicellate and other sessile.
Sessile spikelet about 4 mm long; callus bearded; lower glume coriaceous except at apex, with 4-5 transversely rugose lines on dorsal part, margins keeled and winged, wings minutely ciliate; upper glume boat-shaped, 1-keeled; lower lemma slightly shorter than the spikelet, upper margin shortly ciliate; upper lemma deeply 2-cleft, the awn 15-20 mm long, protruding from the sinus; anthers about 2 mm long. Pedicellate spikelet awnless, sometimes reduced to only the glumes.
NANTOU: Nanhua, Suzuki 5900. KOAHSIUNG: Chishan, Hsu s. n. July 7, 1968.
Distributed from India, Burma, Malaya, Thailand to China.
A very variable species which is found in both wet or dry habitats.
Ischaemum akoense may only be an extreme form of this species.