23a. Fimbristylis dichotoma subsp. dichotoma
两歧飘拂草(原亚种) liang qi piao fu cao (yuan ya zhong)
Scirpus dichotomus Linnaeus, Sp. Pl. 1. 50. 1753; Fimbristylis annua (Allioni) Roemer & Schultes; F. dichotoma f. annua (Allioni) Ohwi; F. dichotoma var. tikushiensis (Hayata) T. Koyama; F. dichotoma f. tomentosa (Vahl) Ohwi; F. diphylla (Retzius) Vahl; F. diphylla var. annua (Allioni) C. B. Clarke; F. tikushiensis Hayata; F. tomentosa Vahl; S. annuus Allioni; S. diphyllus Retzius.
Culms (5-)15-50 cm. Leaves slightly shorter to sometimes slightly longer than culm; leaf blade linear, 1-2.5 mm wide. Inflorescence a compound or rarely simple anthela. Spikelets 4.5-8.5 mm. Fertile glumes 2.2-3 mm. Nutlet obovoid to broadly so, 0.6-1.2 mm, with 5-11 vertical rows of transversely oblong epidermal cells, apex rounded to obtuse. Fl. and fr. Jul-Oct. 2n = 10, 20.
Paddy fields, open grasslands, shallow water in marshes; near sea level to 2100 m. Anhui, Chongqing, Fujian, S Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, E Nei Mongol, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xisha Qundao, SE Xizang, Yunnan, Zhejiang [Afghanistan, India, Japan, Korea, Kyrgyzstan, Nepal, Pakistan, Papua New Guinea, Sri Lanka, Thailand, Uzbekistan, Vietnam; Africa, SW Asia, Australia, Central, North, and South America, Indian Ocean islands, Madagascar, Pacific islands].
Within Fimbristylis dichotoma subsp. dichotoma two varieties could be recognized in China, i.e., F. dichotoma var. dichotoma and F. dichotoma var. tikushiensis. The latter can be separated by its mostly single spikelets that are 7.5-8.5 mm in contrast to var. dichotoma with spikelets clustered and 5.5-8 mm. In var. tikushiensis styles of the fruiting state are elongated exposing them beyond the glume apex, but in var. dichotoma styles at the fruiting state are still enclosed by the subtending glume. In typical subsp. dichotoma plants tend to be biennials or short-lived perennials often with a very short rhizome, whereas in var. tikushiensis plants are typically annual without a rhizome.
In NE China, Korea, and Japan another annual phase of Fimbristylis dichotoma subsp. dichotoma occurs, in which spikelets are as a rule solitary and stems and leaves tend to be hairy and softer. This annual plant has been named F. dichotoma var. tentsuki T. Koyama and if recognized as a variety has often been misidentified as F. annua (e.g., by Nakai, Bot. Mag. (Tokyo) 36: 20. 1922; Kükenthal, Acta Horti Gothob. 5: 109. 1930) and also misidentified as F. depauperata as mentioned above. It is quite possible that this annual plant does not constitute a real taxon but may possibly be a fruiting plant of a first-year seedling of var. dichotoma. It appears in the northern part of the geographical area of subsp. dichotoma, where it cannot survive through the winter and only occurs as an annual. In southern areas it may become biennial or a short-lived perennial developing a short rhizome and is treated as subsp. dichotoma (F. dichotoma var. floribunda Miquel). For more exhaustive treatment of the nomenclature, as well as misapplication of the various names in Asia, see T. Koyama (J. Jap. Bot 63: 86-95, t. I-III. 1988).