黍束尾草 shu shu wei cao

Rottboellia zea C. B. Clarke, J. Linn. Soc., Bot. 25: 86. 1889; R. thyrsoidea Hackel; Thyrsia thyrsoidea (Hackel) A. Camus; Thyrsia zea (C. B. Clarke) Stapf.

Perennial, forming large clumps. Culms stout, up to 2 m or more tall, ca. 10 mm in diam., simple or rarely branched, nodes bearded. Leaf sheaths keeled, glabrous; leaf blades linear-lanceolate, rather stiff, tough, 30–60 × 1–2 cm, hairy near ligule on adaxial surface, margins ciliate near base; ligule 1–2 mm, margin ciliate. Inflorescence a large ovate-oblong panicle, 25–40 cm, with many racemes arranged in whorls. Lower racemes pedunculate, up to 10 cm; rachis internodes broadly cuneate, angled, ribbed, finely scaberulous. Sessile spikelet 3.5–4 mm; lower glume ovate, papery, flat on back, marginally 2-keeled, keels narrowly winged, wings scabrid-hispidulous, apex obtuse; upper glume lanceolate, acute; lower floret sterile, palea absent; upper floret with palea as long as lemma, 2 styles arising separately from ovary apex, not elongate. Pedicelled spikelet similar to sessile but slightly smaller; pedicel resembling internode but shorter. Fl. and fr. autumn.

Grassy hill slopes; 300–1000 m. Guangxi, Yunnan [Bhutan, India, Myanmar, Nepal, Thailand, Vietnam].

Rottboellia zea (February 1889) has priority over R. thyrsoidea (April 1889), as was acknowledged by Hackel (in A. Candolle & C. Candolle, Monogr. Phan. 6: 690. 1889).

This species is anomalous in the genus because of its elongate inflorescence of many whorled racemes.