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, occasionally climbing, undershrubs, shrubs, or rarely trees. Leaves opposite or alternate, often bistipulate, rarely entire. Flowers often showy, regular or irregular, hermaphrodite, usually sub-umbellate, or solitary and axillary, rarely cymose or racemose. Sepals 5, seldom fewer, free, or sometimes united to the middle, imbricate or valvate, the upper one spurred in some genera. Petals 5, or by abortion fewer or quite absent, imbricated or contorted. Disk of 5 glands, opposite the sepals, or eglandular. Stamens usually 10, rarely more or fewer. Fruit either capsular, of 3 to 5 1-seeded carpels terminating-in long slender awns and separating from the placentiferous axis with elasticity, or 2- to many-seeded with a dorsal loculicidal dehiscence, or consisting of 3 to 5 indehiscent indurated cocci separating from the axis, rarely baccate. Seeds variable, with or without albumen. There are 16 genera and about 750 species, found in nearly all parts of the world, but especially numerous in South Africa.