Fimbristylis autumnalis (Linnaeus) Roemer & Schultes subsp. tainanensis (Ohwi) T. Koyama; F. microcarya F. Mueller var. tainanensis (Ohwi) H. Y. Liu.
Perennials. Rhizomes short, ascending. Culms laxly tufted, 40-60 cm tall, compressed 3-sided or apically ± 2-angled, basally leaved. Leaf sheath ± 2-ranked, pale or tinged brown, mouth obliquely truncate and with a fringe of short pubescence; ligule short, ciliate; leaf blade 3-5 mm wide, ± flat, subrigid, scabrous toward subabruptly acute apex. Involucral bracts 2-4, basal one linear and equaling inflorescence. Inflorescence a compound or in part decompound anthela, 3-4 cm, with many dense spikelets; rays many, 1-2 cm, compressed. Spikelets solitary or in groups of 2 or 3, chestnut-brown to light brown, oblong to narrowly ovoid, 4-6 × 1.5-2 mm, 5-10-flowered, apex subacute. Glumes pale brown with chestnut-brown striae on both surfaces, oblong to oblong-ovate, 2-2.5 × 1-1.2 mm, 3-veined, apex with an acute costa. Stamens 3. Nutlet pale yellow, obovoid to broadly ovoid, 0.7-0.8 × ca. 0.7 mm, 3-sided, indistinctly cancellate, verruculose; persistent style ca. 2 mm, base conically thickened.