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 gravelly mountain lake-bottoms. The plant has the rosette habit. The rootstock is fleshy, short, and bears slender stolons. The fibres of the roots are white and cellular. The simple aerial stem is a more or less leafless scape. The radical leaves are submerged, more or less cylindrical, with two hollow, parallel cavities or tubes, linear, blunt, entire, bent-back. The scape is hollow and bears bracts below. The flowers are pale-blue, distant, in a loose raceme, aerial or raised above the water. The flower-stalks are short. There are short, oblong, blunt bracts. The calyx is inversely conical, round, with short, blunt lobes. The corolla-segments are linear, blunt, the upper ones are erect, the lower longer. The anthers are included. The capsule is club-shaped and inclined. The plant is 1-2 ft. in height, flowering in July and August, and is a herbaceous perennial.