1. Glyceria acutiflora Torrey subsp. japonica (Steudel) T. Koyama & Kawano, Canad. J. Bot. 42: 869. 1964.
甜茅 tian mao
Hemibromus japonicus Steudel, Syn. Pl. Glumac. 1: 317. 1854; Glyceria japonica (Steudel) Miquel.
Perennial. Culms ascending from long prostrate base, rooting at lower nodes, 40–70 cm tall, 1.5–3 mm in diam. Leaf sheaths keeled, smooth, longer than internodes; leaf blades flat, flaccid, 5–15 cm × 4–5 mm, slightly scaberulous, apex acute; ligule 4–7 mm. Panicle narrow, 15–30 cm, base often included in uppermost leaf sheath; branches 2 at lower nodes, unequal with one very short, erect, unbranched, bearing only one spikelet, panicle racemelike toward apex. Spikelets linear, cylindrical, 2.5–4.2 cm, florets 7–14, pale green; glumes oblong to lanceolate, membranous, 1-veined, lower glume 2.5–4 mm, upper glume 4–6 mm, apex subacute; lemmas lanceolate, 7–9 mm, herbaceous, 7-veined, scaberulous, apex membranous, acute or slightly tridentate; palea longer than lemma by 0.7–1.4 mm, keels thick, narrowly winged, hyaline between keels down midline, exposed apex 2-toothed. Stamens 3, anthers 0.8–1.3 mm. Fl. Mar–Jun. 2n = 20.
Rice fields, streams, ditches, forming colonies; 400–1000 m. Anhui, Fujian, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang [Japan, Korea; North America].
Glyceria acutiflora subsp. acutiflora occurs in E North America. It is tetraploid (2n = 40) and can be distinguished morphologically by its longer anthers (1.5–1.8 mm), narrower, membranous lemma apex, and frequently longer palea (extended up to 2 mm beyond lemma apex).