37. Cyperus tenuiculmis Boeckeler, Linnaea. 36: 286. 1870.
四稜穗莎草 si leng sui suo cao
Perennials. Rhizomes short, woody. Culms laxly tufted, 40-75 cm, slender, triquetrous, smooth, basally with several leaves, base slightly swollen. Leaves shorter than culm; sheath brown, ± long; leaf blade 2-6 mm wide, margin revolute. Involucral bracts (2 or)3, leaflike, basalmost longer than inflorescence. Inflorescence a simple or rarely compound anthela; rays 3-7, 1-10 cm. Spikes ovoid, with 3-14 spikelets. Spikelets laxly arranged, narrowly linear-ovoid to linear, 1-2 cm × 1.5-2 mm, subquadrangular, obliquely spreading but subspreading after anthesis, 6-14-flowered; rachilla flexuose, wings blackish brown and caducous. Glumes yellow to yellowish brown on both surfaces, slightly lax, elliptic, ca. 4 mm, membranous, 7-9-veined, keel green, apex obtuse. Stamens 3; anthers linear; connective slightly prominent beyond anthers. Style long; stigmas 3. Nutlet black, ellipsoid to obovoid, 3-sided, concave on 3 sides, ca. 1/2 as long as subtending glume, densely puncticulate. Fl. and fr. May-Nov. 2n = 88.
Mountain slopes, open grasslands, streamsides, wet places under sparse forests, fields; 200-1600 m. Fujian, Guangdong, Guangxi, Hainan, Sichuan, Taiwan, Yunnan, Zhejiang [Bhutan, Cambodia, India, Indonesia, S Japan, Laos, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Sri Lanka, Thailand, Vietnam; tropical Africa and Australia, Pacific islands].
Cyperus tenuiculmis was misidentified as C. zollingeri Steudel by Tang and F. T. Wang (Fl. Reipubl. Popularis Sin. 11: 137. 1961).