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 very rarely shrubs, glaucescent or pilose; juice often coloured. Leaves alternate, or the floral occasionally opposite, entire, lobed, or finely divided, destitute of stipules. Peduncles 1-flowered, or rarely subumbellate, often lengthened, terminal, or from the axils of the upper leaves. Flowers regular or irregular. Sepals 2 or 3, rarely 4, very caducous. Petals 4 to 6, occasionally more, in two or three series, often crumpled. Stamens numerous, free, or few, and with connate filaments. Ovary free, 1-celled, with many-ovuled parietal placentas, or 2- or many-celled. Styles short or obsolete; stigmas radiating or lobed. Ovules anatropous. Capsule dehiscing by pores or valves, more rarely indehiscent. Seeds few or many, albuminous. The species of this order are widely distributed, chiefly in the temperate parts of the northern hemisphere. Narcotic, acrid, or poisonous plants. Opium is the product of a species of Poppy. Chiefly valuable to the gardener for the showy annuals it abounds in.