Nuphar microphylla Fernald

Rhizomes 1-2 cm diam. Leaves mostly floating, occasionally submersed; petiole flattened to filiform. Leaf blade abaxially often purple, adaxially green to greenish purple, broadly elliptic to ovate, 3.5-10(-13) × 3.5-7.5(-8.5) cm, 1-1.5 times as long as wide, sinus 2/3 or more length of midrib, lobes divergent and forming V-shaped angle; surfaces abaxially glabrous to densely pubescent. Flowers 1-2 cm diam.; sepals 5(-10), abaxially green to adaxially yellow toward base; petals broadly spatulate and thin, or notched and thickened; anthers 1-3 mm, shorter than filaments. Fruit yellow, green, brown, or rarely purple, mostly globose-ovoid, occasionally flask-shaped, 1-2 cm, smooth basally, faintly ribbed toward apex, deeply constricted below stigmatic disk, constriction 1.5-5 mm diam.; stigmatic disk red, 2.5-7 mm diam., with 6-10 deep crenations; stigmatic rays 6-11, linear, terminating 0-0.2 mm from margin of disk. Seeds ca. 3 mm. 2 n = 34.