细毛臂形草 xi mao bi xing cao

Brachiaria subquadripara var. setulosa S. L. Chen & Y. X. Jin; Urochloa fusiformis (Reeder) Veldkamp.

Annual. Culms loosely tufted, branching, 30–50 cm tall, basal internodes purplish, pubescent, upper internodes glabrescent. Leaf sheaths densely pilose; leaf blades lanceolate, 4–5.5 × 0.7–0.9 cm, densely pilose, base rounded, margins cartilaginous, scaberulous and spinulose, apex acute; ligule 0.5–1.5 mm. Inflorescence axis 6–8 cm, pubescent; racemes 4–5, 3–5 cm, narrowly ascending to suberect, lowermost with basal racemelets; rachis triquetrous, 0.3–0.4 mm wide; spikelets single, their own length apart or overlapping; pedicels setose. Spikelets narrowly elliptic, 3.8–4 mm, with a 0.3–0.5 mm basal stipe, herbaceous, softly pubescent, strongly veined, apex sharply contracted, shortly acuminate; lower glume 1/2 spikelet length, clasping, 3–5-veined, obtuse; upper glume as long as spikelet, 5-veined, cross veinlets toward apex; lower lemma similar to upper glume, back flat to slightly sulcate; upper lemma shorter than spikelet, inconspicuously punctate-rugulose, apex acute, minutely scabrous-pubescent, slightly crested.

Mountain slopes. Yunnan (Yongsheng) [Indonesia, New Guinea, Philippines].

The Chinese population of this little-known species has larger spikelets than specimens from tropical SE Asia, but is otherwise typical. In the Philippines the spikelets have an apical fringe of longer hairs, but other Brachiaria species are also variable in this character. The very slender, triquetrous rachis and contracted, acuminate spikelet apex are unusual in the genus.