5. Ischaemum polystachyum J. Presl in C. Presl, Reliq. Haenk. 1: 328. 1830.
簇穗鸭嘴草 cu sui ya zui cao
Ischaemum digitatum Brongniart; I. duthiei Stapf ex Bor; I. fasciculatum Brongniart.
Perennial, rhizomatous. Culms loosely tufted, sometimes stoloniferous and rooting at lower nodes, 60–100 cm tall, nodes bearded or glabrous. Leaf sheaths glabrous or sparsely to densely pilose with tubercle-based hairs; leaf blades broadly linear, 5–20 × 0.5–1.5 cm, pubescent, rarely glabrescent, base rounded to subcordate, apex acute; ligule 1–2 mm. Racemes (2–)3–6 or more, mostly terminal, subdigitate, 2–9 cm; rachis internodes and pedicels broadly linear, triquetrous, ciliate on outer angle, shortly ciliate on inner angles. Sessile spikelet lanceolate, 4–5 × 1.2–1.4 mm; lower glume leathery with expanded rounded flanks below middle, herbaceous, strongly veined and sharply 2-keeled above, glabrous or villous, keels usually winged, apex 2-toothed; upper glume attenuate into mucro or awnlet to 2 mm; awn of upper lemma 1.2–1.5 cm. Pedicelled spikelet laterally compressed, similar to sessile, upper lemma awned.
Moist places on grassy plains and hillsides; 100–400 m. Guangdong, Guizhou, Yunnan [India, Malaysia, Myanmar, Sri Lanka, Thailand; Africa, Mauritius, Pacific Islands].
This is a widespread, polymorphic species, long known by different names in various parts of its range.