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..
[Desmodium Desv. Journ. Bot. (II.) 1: 122. pl. 5, /. 15. 1813.] Perennial herbs, sometimes woody at the base, erect, ascending or trailing, with stipellate 3-foliolate or in some species 1- or 5-foliolate leaves, and usually small flowers in terminal or axillary compound or simple racemes or panicles. Calyx-tube short, its teeth more or less united into 2 lips, the upper one variously 2-toothed, the 3 lower teeth acute or attenuate. Standard oblong, ovate or orbicular, narrowed or rarely clawed at the base; wings obliquely oblong; keel nearly straight, obtuse. Stamens monadelphous or diadelphous (9 and 1); anthers all alike. Ovary sessile or stalked; ovules 2-00. Loment flat, sessile or stalked, several jointed, the joints mainly coriaceous and pubescent or muricate, indehiscent or rarely partially dehiscent, readily separable. [Named for Dr. Brandus Meibom, died at Helmstadt, 1740.]
A genus of about 160 species, natives of warm and temperate North and South America, South Africa and Australia. Besides the following, about 20 others occur in the southern and southwestern States. Our species are known as Tick-trefoil, or Tick-seed. Type species: Hedysarum cana-dense L.
* Loment not constricted above, deeply constricted below, long-stalked; leaflets broad.
Panicle arising from the base of the plant; peduncle usually leafless.
Leaves crowded at its base.
Leaves scattered along the stem.
** Loment constricted on both margins, more deeply below than above.
† Stems trailing or reclining.
Leaflets orbicular or nearly so.
Leaflets 1' long or less, glabrate, coriaceous; stipules subulate.
Leaflets 1' - 2' long, thinnish, usually quite pubescent; stipules ovate.
Leaflets ovate or oval.
Corolla whitish; leaves yellowish green; stipules broadly ovate.
Corolla purple; leaves dull green; stipules subulate.
■ft Stems erect or ascending.
Leaves sessile or nearly so; leaflets linear or lanceolate.
Leaflets narrowly linear; joints of the loment usually concave on the back.
Leaflets broad (except in races of M. paniculata).
I. Joints of the loment notably longer than broad.
Leaflets obtuse, rough-pubescent, yellowish green.
2. Joints of the loment little longer than broad.
(a.) Loment distinctly long-stalked in the calyx.
Plants glabrous, or nearly so (except in races of M. paniculata).
Leaflets lanceolate or oblong.
Leaflets broadly ovate or oval, glaucous beneath.
Plants pubescent or scabrous.
Leaflets thick, coriaceous.
Leaves villous and reticulated beneath.
Leaves velvety-pubescent beneath.
Leaflets scarcely coriaceous, appressed-pubescent or villous beneath
(b.) Loment sessile in the calyx, or nearly so.
Loment-joints 4-7; flowers numerous, showy.
Leaflets coriaceous, strongly reticulated beneath.
Leaflets not coriaceous, scarcely reticulated beneath; loments numerous.
Leaflets scabrous, 1' - 2' long.
Leaflets not scabrous, 5"-10" long.
Plant nearly glabrous throughout.
Stem pubescent; leaflets and petioles ciliate.