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..
Annual or perennial vines, rarely erect herbs, with pinnately 3-foliolate stipellate leaves, and axillary racemose flowers. Calyx 5-toothed or 5-lobed, or the 2 upper teeth more or less united. Standard orbicular, recurved, spreading or somewhat contorted; wings mainly obovate, equalling or exceeding the standard; keel spirally coiled, linear or obovoid. Stamens diadelphous (9 and 1); anthers all alike. Style longitudinally bearded; stigma oblique or lateral; ovary sessile or nearly so; ovules 00. Pod linear, straight or curved, 2-valved, several-seeded, tipped with the persistent style. Seeds mostly with rounded ends. Rachis thickened at the bases of the pedicels. [Ancient name of the Kidney Bean.]
About 170 species, natives of warm and temperate regions. Besides the following, about 12 others occur in the southern and southwestern states. Type species: Phaseolus vulgaris L.
Dolichos polystachyus L. Sp. Pl. 726. 1753. Phaseolus perennis Walt. Fl. Car. 182. 1788. Phaseolus polystachyus B.S.P. Prel. Cat. N. Y. 15. 1888.
Climbing over bushes, or trailing, from a perennial root, finely pubescent, branched, 4°-15° long. Stipules lanceolate, deciduous; leaflets broadly ovate or nearly orbicular, acute or acuminate at the apex, rounded at the base, 2-4' long, the terminal one often slightly cordate, the lower ones unequal-sided; racemes axillary, usually numerous, peduncled, 4'-12' long, narrow, loosely-flowered; pedicels 2"-4" long, minutely bracted at the base; corolla purple, about 4" long; pods stalked, drooping, somewhat curved, flat, 1 1/2'-2 1/2' long, 4"-5" wide, 4-6-seeded, glabrous or nearly so; seeds chocolate-brown, 3"-4" long.