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, shrubs, or trees. Leaves alternate, whorled, or less frequently opposite, simple or compound, exstipulate. Flowers sessile on the expanded peduncle or receptacle, and surrounded by a number of more or less leafy bracts termed the involucre. Receptacle with or without bracteoles or bristles between the florets. Calyx superior; limb none, or feathery, or scaly, and termed the pappus. Corolla variable in the different tribes. Stamens 4 or 5; anthers usually connate. Style filiform, with a bifid stigma. Fruit dry and indehiscent, containing one erect albuminous seed. A vast order comprising about 1,000 genera and 8,000 species, occurring in all parts of the world. The ornamental species are so numerous that we must confine ourselves to descriptions of a selection of the better known ones which are worthy of cultivation, and merely mention the names of those of secondary importance. They may be conveniently divided into three large groups, and these again into several tribes.