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.
Twining or trailing herbs, rarely shrubs or trees. Leaves alternate, entire or lobate. Flowers in axillary or terminal racemes or solitary. Calyx of 5 equal or unequal persistent imbricate sepals. Corolla hypogynous, regular, salver-shaped or tubular, 5-lobed or nearly entire, plaited, convolute or twisted in bud. Stamens 5, inserted on the corolla-tube; filaments often dilated at the base. Capsule 1-to 4-celled, few-seeded. A large order of highly ornamental plants, chiefly natives of tropical countries-There are 40 genera and about 650 species. The curious leafless genus Cuscuta is referred here. The species are annual parasites with slender thread-like stems and clusters of small flowers. Two species are indigenous, one of which (C. Epithymum) is common on Heather and other dwarf plants, and the other (C. Europaea) is a stouter plant, much rarer, and usually found on Nettles or Vetches. One or two exotic species have been introduced with Flax and Clover seeds, and have often much damaged the crops they prey upon.