1. Aponogeton lakhonensis A. Camus, Notul. Syst. (Paris). 1: 273. 1910.
水蕹 shui weng
Aponogeton pygmaeus K. Krause; A. taiwanensis Masamune.
Rhizome obovoid or elongated, to 2 cm, often with filament remnant of sheath. Petiole 9-15 cm in submerged leaves and 40-60 cm in floating leaves; leaf blade narrowly ovate to linear, 4-6 × 1-2 cm, herbaceous, with 7-9 primary veins at base, base cordate or rounded, margin entire, apex rounded or with a blunt tip. Inflorescence to ca. 5 cm, pedunculate. Flowers bisexual. Perianth segments 2, yellow, slightly obovate, ca. 2 mm. Stamens 6; filaments broadened toward base. Carpels slightly united near base, with 4-6 ovules per carpel. Fruit ovoid, 2-3 mm, with a short terminal beak. Fl. Apr-Oct.
Paddy fields, ponds, streams. Fujian, Guangdong, Guangxi, Hainan, Jiangxi, Taiwan, Yunnan, Zhejiang (Longquan) [Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Thailand, Vietnam].
The specimens of this species were incorrectly named Aponogeton natans (Linnaeus) Engler & Krause, but the latter has reddish or purple flowers, filaments not broadened, and a longer beak. The relationship between A. lakhonensis and A. natans needs to be further studied.