Myriophyllum tuberculatum Roxb.

Aquatic or semi-aquatic. Stems mostly much branched. Immersed leaves in whorls of 4-5, 2½-4 by 1-1½ cm in outline, with 8-25 pairs of rather weak, ligulate, acute or shortly mucronate segments 10-20 mm long. Aerial leaves in the lower part as the immersed ones, upper ones finally alternate, with less and shorter lobes, uppermost almost entire, 5-20 by 1-3 mm, patent or recurved. Flowers solitary, sessile, in the middle and upper leaf-axils, mostly all ☿, rarely the upper flowers ♂, sometimes the lower ♂. Bracteoles ± rhomboid, serrate, acute, c. 1.2 by 0.8 mm. Sepals very small, ± orbicular, entire or finely serrate, erect, 0.1-0.25 by 0.1-0.25 mm. Petals in and after anthesis patent and finally recurved-circinnate, not soon caducous, c. ½-1½ mm long. Stamens 4; anthers elliptic-oblong, c. ½-1 by 0.2-0.3 mm. Styles 0.1-0.2 by 0.2 mm, scarcely recurved, with capitate stigmas. Fruit quadrangular, between the sharp and alternisepalous ribs slightly concave, indistinctly 4-sulcate, aculeate, finely foveolate, c. 2-3½ by 2-3½ mm.

In shallow, stagnant water at low altitude.