This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The habitat of this plant is ponds, ditches, fen-ditches, still water. The plant has the aquatic habit. The stems are stolons. The leaves are numerous, sword-like, tapering, triangular, spinous, fringed with hairs or coarsely toothed, spreading, rigid, brittle, deep-green, with many nerves. The flowers are white, borne on flattened flower-stalks, which are axillary, short, and stout. The flowers rise to the surface and flower. The fruit is green, bent down at right angles to the stalk, flagon shaped, 6-angled, with carpels that separate. The seeds are mucilaginous. The plant is 6-18 in. in height, flowering- from June to August, and is a herbaceous perennial.
The habitat of this plant is ponds, ditches, canals, streams. The habit is aquatic. The plant is dark-green, but transparent. The stems are long, brittle, round, rooting at the nodes, branched. The leaves are in whorls of 3-4, numerous, stalkless, close, oval or oblong, linear or lance-shaped, blunt, with small, coarse teeth. The flowers are greenish-purple, floating, with a long, slender tube, 3-8 in., which is a bifid spathe, with a stalkless ovary below. Only the female flowers are known in this country, except at Edinburgh, where the male flower has been found. The sepals are broad, nearly equal, boat-shaped, tinged with green and pink externally, hooded, bent inwards. The petals are oblong, bent-back, flat, transparent. The stigma is long, round in section, notched. There are no anthers. The anther-stalks are at first curved outwards, erect, linear, blunt. The plant is 1-4 ft. in length or height, flowering from July to October, and is a herbaceous perennial.