Description from Flora of China
Utricularia japonica Makino; U. neglecta Lehmann; U. sacciformis Benjamin; U. siakujiiensis Nakajima ex H. Hara; U. tenuicaulis Miki; U. vulgaris var. tenuicaulis (Miki) F. T. Kuo ex J. Y. Hsiao.
Perennials, suspended aquatic. Rhizoids usually present, filiform, bearing numerous short dichotomously divided branches. Stolons filiform, branched. Traps on leaf segments, stalked, ovoid, 0.5-2.5 mm, mouth lateral or basal; appendages 2, dorsal, simple or branched, setiform, with shorter simple lateral setae. Leaves numerous, 1.5-4 cm, divided from base into 2 ± equal primary segments; primary segment ovate, elliptic, or ovate-oblong in outline, pinnately divided into secondary segments; secondary segments dichotomously divided into further segments; ultimate segments capillary, slightly flattened, margin sparsely denticulate, apex and teeth setulose. Inflorescences erect, (5-)10-30 cm, 3-8-flowered, glabrous; peduncle terete, 1-2 mm thick; scales 1-3, similar to bracts; bracts basifixed, suborbicular, 2-5 mm, base auriculate, apex rounded and obscurely tridentate. Pedicel erect at anthesis but decurved in fruit, terete, 1-2.5 cm; bracteoles absent. Calyx lobes ovate, 3-4 mm, subequal; lower lobe apex emarginate; upper lobe apex rounded. Corolla yellow, 1.2-1.5 cm; lower lip transversely elliptic, base with a prominent swelling, apex rounded to retuse; spur broadly conic, considerably shorter than corolla lower lip, slightly curved, apex obtuse; palate glabrous; upper lip broadly ovate, apex retuse. Filaments ca. 2 mm, curved; anther thecae distinct. Ovary globose, densely covered with sessile glands; style evident; stigma lower lip semicircular and ciliate, upper lip very short or obsolete. Capsule globose, 3-4 mm in diam., circumscissile. Seeds prismatic, 0.5-0.6 × 0.5-0.7 mm, 4-6 angled, narrowly winged on all angles; seed coat with small prominent slightly elongate reticulations. Fl. Jun-Nov, fr. Jul-Dec. 2n = 40, 44.
Lakes, pools, river backwaters, ditches, rice fields; near sea level to 2500 m. Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, S Shaanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, India, Indonesia, Japan, Kashmir, Korea, Mongolia, Myanmar, Nepal, Pakistan, Papua New Guinea, Philippines, Russia (Sakhalin), Sri Lanka; Africa, SW Asia, Australia, Europe, Pacific islands (New Zealand)].