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 river-banks, watery places. The plant is erect in habit. It is roughly hairy all over. There is a branched rootstock. The roots are fibrous and fleshy. The stem is stout, angular, branched, broadly winged at the top. The leaves are ovate to lance-shaped, narrow below, the radical leaves with a long winged leaf-stalk, are shortly - stalked, and running down the stem. The flowers are yellowish - white or purple (5. patens), in racemes or scorpioid cymes in pairs, drooping. The sepals are narrow to lance-shaped, spreading, more downy in the purple-flowered type. The nutlets are shining. The plant is 1-3 ft. high, flowering in May and June, and is a herbaceous perennial.
The habitat of this plant is watery or wet places. The habit is prostrate, then ascending. The rootstock is short, and there are no stolons. The plant has a felt of distant appressed hairs. The stem is much branched, round, with a line running down the stem, the branches slender. The leaves are bright, shining-green, the radical ones spoon-shaped to oblong, polished. The stem-leaves are linear to oblong, with a rounded tip, blunt or notched, narrowed to the stalkless base. The flowers are bright-blue, in a raceme, or long cyme, slender, leafy below. The sepals have straight, closely pressed hairs, and are blunt, triangular, oblong to ovate, as long as the tube. The corolla has a yellow disk or centre. The style is not so long as the calyx. The nutlets are black, short, broad, bordered, not keeled in front. The plant is 6-18 in. in height, flowering between May and August. It is a herbaceous perennial.