Spikerush

Koyama in Dassanayake & Fosberg (eds.), Fl. Ceylon (1985) distinguishes besides E. congesta subsp. congesta also subsp. japonica (Miq.) T. Koyama, however, with almost identical distributions.

Tufted annual, 17-30 cm. Roots white, fibrous. Stem 0.7-1 mm diam., angular, angles separated by deep grooves, to nearly terete, basal parts reddish. Sheaths ephemeral, lower closed sheath short; upper 10-25 mm, scarious, at least basally reddish, mouth margin oblique. Spike 4-6 mm, ellipsoid or ovoid to globular, brownish green, of 30-100 tightly imbricate glumes; basal glume sterile, clasping, longer and wider than the other; glumes 1.5-1.8 mm, not in protruding spiral rows, cymbiform, wide, obtuse, green mid-nerve not reaching apex, sides nerve-less, scarious, reddish-brown towards apex. Perianth bristles 6-7, longer than nut (incl. stylopodium), light brown; stamens 2, anther 0.6-0.7 mm; stigmas 3. Nut 0.8-1 x 0.5-0.6 mm (excl. stylopodium), obovoid, yellowish brown, obscurely reticulate, glossy; stylopodium 0.2-0.3 x 0.3 mm, clearly constricted from nut, trigonous, sides concave.

Nepal, India, Indo-China, China, Japan.

Distribution: From Pakistan, Kashmir and NW India to China and Japan, Philippines and Malaysia.

200-2300 m

Swamps, rice fields.

E. subvivipara Boeck. in Linnaea 36: 424. 1870; C.B. Clarke, Ill. Cyperaceae: tab. 37, figs. 13-16 (1909, as E. subvivipara).