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.
Leaves alternate, often spinescent. Involucral bracts usually imbricate and prickly. Florets, in most genera, all tubular; tube slender, ventricose. Lobes of the style with a swelling or ring of hairs at their base.