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.
A very extensive genus of herbs or dwarf often spiny shrubs with unequally pinnate leaves and racemose or spicate seldom umbellate flowers. Calyx tubular; teeth 5, nearly equal. Petals narrow, with long claws. Pod usually 2-celled longitudinally by the intrusion of a thin membrane from the dorsal suture. There are between 500 and 600 species, or, according to a recent monograph by Bunge, 900 to 1,000, chiefly from Russian Asia, the Himalayas, and Asia Minor, and extending throughout the Mediterranean region, the mountains of tropical Africa and America, and temperate North America. Few species are generally cultivated, but many more deserve cultivation. The name was applied by the ancients to some plant of this family, probably Orobus vernus.
1. A. alopecuroldes. - An herbaceous perennial about 2 feet high with leaves composed of 21 to 41 ovate-lanceolate petiolulate leaflets and yellow axillary flowers. The elegant foliage of this species forms its chief attraction. A native of Spain, blooming in Midsummer.
2. A. Monspessulanus. - Almost stemless. Leaves hairy, of 31 to 41 leaflets. Flowers purple, on the summit of a peduncle exceeding the leaves. This is a very pretty species and the most common in gardens. A native of Europe, flowering in June or July.
3. A. Hypoglottis. Milk Vetch. - An indigenous dwarf species with from 17 to 25 small hairy leaflets and purplish flowers on long axillary peduncles.
4. A. Onobrychis. - Diffuse or erect. Leaflets 8- to 12-jugate, hairy. Flowers purple, in dense spikes; peduncles longer than the leaves. One of the most beautiful species. A native of Central Europe, flowering in Summer.