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 or annual herbs, rarely shrubs, many of them bearing handsome brightly-coloured flowers. Leaves usually all radical, but when cauline opposite or whorled and exsti-pulate. Calyx inferior, regularly 5-lobed, or less frequently 4- to 9-toothed. Corolla regular, hypogynous, rotate, campanu-late or infundibuliform. Stamens inserted on the corolla-tube and opposite its lobes. Capsule 1-celled, splitting in valves or transversely; seeds attached to a free central placenta, albuminous. There are about 25 genera and 200 species, chiefly from temperate and cold regions.