11. Eleocharis tetraquetra Nees in Wight, Contr. Bot. India. 113. 1834.
龙师草 long shi cao
Perennials. Stolons short or absent. Culms tufted, 25-90(-100) cm tall, ca. 1 mm thick, sharply 4-angled, glabrous. Leaf sheaths 2 or 3, tubular, 7-10 cm, basally purplish red, apically grayish green, mouth truncate, apex shortly triangular and mucronate. Spikelet brownish green, oblong-ovoid, ± narrowly ovoid, or oblong, 7-20 cm × 3-5 mm, slightly oblique, many flowered, apex obtuse to acute. Basal 3 glumes empty; basalmost glume amplexicaul for whole spikelet base; fertile glumes green at middle and pale rust-colored on sides, tightly imbricate, oblong and boat-shaped, 3-4 × 1-1.5 mm, papery, margin narrowly hyaline, apex obtuse. Perianth bristles 6, reddish to brownish, as long as nutlet (including style base), laxly to densely retrorsely spinulose. Stigmas 3. Nutlet pale brown when mature, with a short thick stipe, obovoid to broadly obovoid, ca. 1.2 × 1.5 mm, compressed 3-sided; persistent style base laterally compressed, deltoid, 1/2-2/3 as long and ca. 3/4 as wide as nutlet, surface sometimes mammillate, apex acuminate. Fl. and fr. Sep-Nov.
Pond and ditch margins, riverbanks; 100-1900 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Heilongjiang, Henan, Hunan, Jiangsu Jiangxi, Liaoning, Sichuan, Taiwan, Yunnan, Zhejiang [Afghanistan, Bhutan, India, Indonesia, Japan, Nepal, Pakistan, Papua New Guinea, Philippines, Russia (Far East), Sri Lanka, Thailand, Vietnam; N Australia].