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.
This pant has a tufted habit. The stems are ascending, smooth, fleshy, shiny, like the leaves. The radical leaves are spoon-shaped, rhomboidal, the upper stem-leaves united below into a more or less rounded blade. The flowers are in a raceme, more or less whorled, white, with a few flowers at the base, small. The petals are nearly or quite entire, a little longer than the calyx. The capsule is round, 3-seeded. The seeds are black and round. The plant is 4-12 in. high, flowering from April to June, and is a herbaceous annual.
The habitat of this plant is stream-sides, waste places, and the plant is local. The habit is as in the last. The radical leaves are ovate with a narrow point, the upper leaves are opposite, stalk-less, rounded. The flowers are in a raceme, white or rose, and usually solitary, more numerous and larger than in the last. The petals are chiefly divided into two nearly to the base. The plant is 6-15 in. in height, flowering between May and August, and is a herbaceous annual or perennial.