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.
Trees, shrubs, or herbs of variable habit. The structure of the flowers in this order is very similar to that of the Rosaceae, and in some species so close as to render it a matter of doubt to which order they should be referred. The tendencies in this group are to few stamens, united carpels with numerous seeds, and abundant albumen. 73 genera, including about 540 species, are brought together under this order. They inhabit all countries.