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 moist places, often liable to inundation, just where one might expect to find Water Purslane, but it is very local. The habit is prostrate, or ascending, spreading, simple or branched. The leaves are alternate, linear to lance-shaped, blunt. They are stalkless, and wedge-shaped below, very narrow. The flowers are small, solitary, pink or purplish, in the axils. There are 2 minute, awl-like bracts. The calyx-teeth are short, awl-like. The petals are oblong. There are 6 stamens. The capsule is cylindrical. The plant is 6-18 in. in height, and flowers between June and September, and is a herbaceous perennial.