This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Hispid or hairy annual or perennial herbs, sometimes shrubby at the base, often of prostrate habit. Flowers in bracteate cymes. Calyx 5-lobed to the base. Corolla funnel- or salver-shaped; throat naked, or with 5 tumid folds; limb spreading.
Stamens included. Nuts 4, very hard and bony, smooth or rugose. There are about fifty species, scattered over Europe, North Asia, and North America. The name is a compound of a stone, and a seed, in reference to the stony carpels or nuts. There are three indigenous species: - L. officinale, Gromwell, is an erect perennial with small yellowish white flowers and smooth white nuts; and L. arvense is an erect branching annual with yellowish white flowers and grey wrinkled nuts. The third species is 1. L. purpureo-caeruleum. - This is a handsome perennial with creeping barren and erect flowering stems about a foot high. Leaves scabrid, small, sessile, linear-lanceolate. Flowers about 8 lines in diameter, purple and blue, appearing in Summer. A rare plant in Britain, being confined to a few localities on limestone and chalk hills in the South.
2. L. prostratum, syn. L, fruticosum. - A shrubby evergreen trailer with narrow lanceolate hairy leaves and beautiful deep blue flowers striped with reddish violet. This is one of the most effective dwarf plants in cultivation. It is a native of the South of Europe, and produces its handsome blossoms from May till July.
L. Gastoni is another handsome species of this group.