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.
Perennial tufted herbs with simple flowering stems and terminal cymes. Calyx angular, deeply 5-partite. Corolla funnel-shaped, 5-lobed, with 5 tufts of hairs alternating with the stamens, the latter included. Nuts 4, turbinate, smooth, sessile on a flat receptacle. There are five species, natives of Europe and North Asia. The name is from pulrao, the lungs, in allusion to the supposed efficacy of these herbs in lung complaints; hence the English name Lungwort.
1. P. officinalis. - Leaves radical, ovate-lanceolate, on long petioles, often spotted with light green. Flowers red, changing to blue or purple. This is a common plant in old gardens, and generally known by the blotched leaves, though there is a variety without blotches and another with white flowers. A native of various parts of Europe, and occasionally found in a semi-wild state in Britain.
P. angustifolia, similar to the last, with narrow leaves and pink ultimately bright blue flowers, is believed to be truly indigenous in Hants and Dorset. P. Sibirica is of more slender habit, with uniformly green leaves and deep blue flowers. They all flower in Spring.
Mertensia Virginica, Virginian Cowslip, is an allied perennial plant from 1 to 2 feet high with smooth pale green foliage and pale blue, puiple or white flowers in terminal clusters. It is separated from Pulmonaria on account of the stamens exceeding the corolla-tube, and the nuts being fleshy when fresh. M. maritima is a native species, found on the western coast.
Onosma Tauricum is a handsome tufted herbaceous plant less than a foot high, with lanceolate hispid leaves and large golden yellow flowers in drooping clusters. The stamens exceed the naked corolla, and the nuts are stony. There are several other species, but this is one of the best.