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 calcareous places. The habit is erect. The stem is ascending, much-branched, larger than the Autumnal Gentian (q.v.), with opposite leaves. The flowers are bluish-lilac, the tube of the corolla inversely conical, longer than the calyx, with unequal segments. The capsule is many-seeded. The plant is 2-12 in. in height, and flowers in August and September, being a herbaceous biennial.