Submerged leaves: in whorls of fours and fives, dissected into capillary divisions. Floral leaves: ovate, entire or serrate, usually shorter than the flowers, or sometimes none. Flowers: white, in spikes; petals four; stamens eight. Fruit: splitting at maturity into four bony, oneseeded, indehiscent carpels, which are rounded on the back, with a deep wide groove between them, smooth, or very rarely slightly rugose.

This is an aquatic herb, with submerged, spreading, thready leaves set in whorls of four or five round the thick stems. Sometimes it has floral leaves that are very small and usually shorter than the blossoms. The name Myrio-phyllum is from the Greek and means "myriad-leaved." The flowers are minute and white-petalled and grow in tiny interrupted spikes.