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.
Shrubs or trees, usually evergreen. Leaves simple, alternate, opposite or whorled, exstipulate. Flowers regular, hermaphrodite. Calyx superior or inferior; limb 4- or 5-lobed. Corolla campanulate or urceolate, lobes imbricate. Stamens 4 to 10, hypogynous or epigynous; anthers 2-celled, opening by terminal pores, often furnished with an awn-like appendage. Disk annular, lobed, or glandular. Fruit a berry or capsule, 3- to 5-' celled; cells many- or 1-seeded; seeds small. There are about 75 genera and 1,000 species, mostly from temperate and cold climates. Pyrola, Wintergreen, is an herbaceous genus represented in Britain by three or four species of tufted herbs with radical leaves and terminal racemose spikes of small flowers in which the petals are free or nearly so.