This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Herbs, shrubs, vines or trees, with alternate mostly compound stipulate leaves, and irregular (papilionaceous) perfect or sometimes polygamo-dioecious flowers, mainly in spikes, heads, racemes or panicles. Calyx 4-5-toothed, or 4-5-cleft, the teeth or lobes unequal or equal; sometimes 2-lipped. Petals more or less united, or separate, perigynous or hypogynous, usually consisting of a broad upper one (standard, banner), two lateral ones (wings), and two front ones more or less united (forming the keel); the standard encloses the wings in the bud. Stamens monadelphous; diadelphous, or sometimes separate, 10 in most of the genera, sometimes 9, rarely 5. Pistil 1, simple, superior; ovary mainly 1-celled, sometimes 2-celled by the intrusion of the sutures, or several-celled by cross-partitions; style simple; ovules 1-many; anatropous or amphitropous. Fruit a legume, 1 - many-seeded, dehiscent into 2 valves, or indehiscent, in one tribe a loment. Seeds mostly without endosperm; cotyledons thick.
Genera about 325, species over 5000, most abundant in temperate and warm regions; known also as Papilionaceae and Phaseolaceae, and included by some authors in the Leguminosae.
* The 10 stamens distinct.
Leaves digitate (in ours 3-foliolate), or simple.
** The stamens monadelphous or diadelphous.
Herbs, shrubs, woody vines or trees, the leaves not tendril-bearing.
Pod not a loment, 2-valved or indehiscent.
Foliage not glandular-dotted (except in Glycyrrhiza, which has many-seeded pods).
Stamens monadelphous; anthers of 2 kinds.
Stamens diadelphous (except in Ononis); anthers all alike.
Leaves, in our species, 3-foliolate, rarely 1-foliolate.
Leaves pinnately several-many-foliolate (except in Orophaca)
Foliage glandular-dotted; pod indehiscent, 1-2-seeded; herbs.
Pod a loment; herbs.
Herbaceous vines, or herbs; leaves evenly pinnate, with tendrils.
Vines, ours herbaceous, or herbs; leaves without tendrils.
Tribe 1. Sophoreae.
Our species herbs; flowers racemed.
Trees; flowers panicled.
Tribe 2. Podalyrieae.
Ovary sessile, or nearly so; pod flat in our species.
Ovary distinctly stipitate; pod inflated.
Tribe 3. Genisteae.
Herbs, with simple or 5-11-foliolate leaves.
Leaves simple; pod inflated.
Leaves 5-11-foliolate; pod flattened.
Shrubs with 1-3-foliolate leaves.
Calyx divided into 2 lips; leaves very prickly.
Calyx cleft into 2 lips to about the middle.
Tribe 4. Trifolieae.
Flowers spiked, or capitate; pods curved, or coiled.
Flowers in long racemes; pods coriaceous.
Flowers capitate or umbelled; pods straight, membranous.
Tribe 5. Loteae.
Filaments diadelphous; pods dehiscent.
Leaves pinnate; leaflets sometimes only 1 or 3.
Filaments monadelphous; pods indehiscent or nearly so.
Tribe 6. Psoraleae.
Leaves digitately 3-5-foliolate, or pinnately 3-foliolate.
Leaves pinnately 5-many-foliolate.
Stamens 10 or 9, monadelphous. at least at the base.
Corolla of only 1 petal (the standard).
Corolla of 5 petals, the wings and keel united to the filament-tube.
Stamens only 5, monadelphous.
Tribe 7. Galegeae.
Standard very broad, ovate or orbicular.
Herbs; leaves odd-pinnate.
Pod 4-angled in our species.
High-climbing woody vines.
Trees or shrubs.
Herbs; leaves evenly pinnate.
Standard narrow; our species all herbs.
Pod not prickly; foliage not glandular-punctate.
Keel of the corolla blunt.
Leaves pinnate, or simple.
Pods not flattened, swollen, or one or both sutures intruded.
Pods fleshy, becoming spongy, 2-celled, indehiscent.
Pods not fleshy, dehiscent (epicarp slightly fleshy in Astragalus pectinatus).
Pods not much swollen, leathery or papery.
Pods much inflated, membranous, 1-celled.
Pods flat, both sutures prominent externally.
Leaves not bristle-tipped; pods several-seeded.
Leaves bristle-tipped; pods only 1-2-seeded.
Keel of the corolla acute.
Pod prickly; foliage glandular-punctate.
Tribe 8. Hedysareae.
Leaves 4-foliolate or 2-foliolate.
Leaves 3-foliolate, the terminal leaflets stalked.
Flowers purple, blue or white.
Pod of several joints; leaflets stipellate.
Pod of 1 or 2 joints; leaflets not stipellate.
Tribe 9. Vicieae.
Style slender, with a tuft of hairs at the summit.
Style flattened, bearded along the inner side.
Tribe 10. Phaseoleae.
Style bearded along the inner side; rachis not thickened at the insertion of the flowers; keel of
corolla not curved nor coiled.
Style glabrous, or pubescent below; keel of corolla not curved nor coiled.
Standard spurred at the base.
Standard not spurred.
Flowers blue, purple, purplish, or white.
Leaves odd-pinnate; leaflets 5-7.
Leaves 3-foliolate, rarely 1-foliolate.
Calyx tubular, not bracteolate.
Calyx short, bracteolate.
Style bearded along the inner side; rachis thickened at the insertion of the flowers.
Keel of the corolla spiraily coiled; flowers racemed.
Keel of the corolla strongly incurved; 'flowers purple, capitate.
Keel of the corolla short, slightly incurved; flowers capitate.