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.
Herbs or shrubs with opposite simple exstipulate entire or glandular-toothed leaves, often having transparent glands, and yellow (rarely white) flowers. Sepals 5 or 4, imbricate. Petals of the same number, contorted in the bud. Stamens usually numerous, and united in three or more bundles, rarely few with free filaments. Fruit capsular, composed of 3 to 5 united carpels dehiscing septicidally, or baccate. Seeds few or many, exalbuminous. A small order; as characterised above, it does not include all the exotic genera.