光轴荩草 guang zhou jin cao

Andropogon nudus Nees ex Steudel, Syn. Pl. Glumac. 1: 383. 1854; Arthraxon ciliaris P. Beauvois subsp. nudus (Nees ex Steudel) Hackel; A. hispidus (Thunberg) Makino var. nudus (Nees ex Steudel) Ohwi.

Annual. Culms rather stiff, decumbent, ascending to 50 cm. Leaf sheaths glabrous or tuberculate-hispid; leaf blades narrowly ovate, 2–8 cm × 5–20 mm, glabrous on both surfaces, base amplexicaul, margins scabrid or pectinate-setose at base, apex sharply acuminate to caudate; ligule 2–3 mm. Racemes very slender, 3–9, often rebranched and hence up to 20, 2–8 cm, suberect when young, stiffly divergent at maturity; rachis internodes 4/5 as long to equaling spikelets, glabrous. Sessile spikelet 3–4.5 mm; lower glume linear-lanceolate, leathery, strongly convex, margins not inflexed, back minutely granular, obscurely 6–7-veined below middle, veins scabrid above middle, apex acute; upper glume with acute apex; awn 5.7–9 mm. Anthers 3, 0.4–1 mm. Pedicelled spikelet absent; pedicel 1–2 mm, glabrous.

Swamps, shady places, roadsides; 1200–1300 m. Yunnan [India, Malaysia, Myanmar, Thailand; SW Asia (Oman)].

When anthers are absent, Arthraxon nudus is best distinguished from A. hispidus by its very slender racemes of narrow spikelets spaced almost their own distance apart. The racemes finally spread divaricately as they disarticulate.