Aquatic leaves opposite, elliptic to oblong to 4 cm long. The leaves on stems above water are smaller, narrower and darker.
Flowers are bluish-white to white, and have two lips. They grow from the axils where the leaves meet the stems.
The fruit is a capsule to 9 mm long covered with hairs especially near the top.
Hygro – moist, wet; phil – loving; poly – many, sperma – seed: that is, a “wet-loving plant with a fruit that contains many seeds ”
Photo: Robert Whyte