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..
[AmphicÀrpa Ell. Journ. Acad. Phil 1: 372. 1817.] Twining perennial vines, with pinnately 3-foliolate leaves, small white, violet or purple flowers in axillary racemes, and also solitary apetalous fertile flowers in the lower axils or on the slender creeping branches from the base. Calyx of the petaliferous flowers tubular, 4-5-toothed. Standard obovate, erect, folded around the other petals; wings oblong, curved, adherent to the incurved obtuse keel. Stamens diadelphous (9 and 1); anthers all alike. Style filiform, not bearded. Pods from the upper flowers linear-oblong, several-seeded, 2-valved, those from the lower obovoid, fleshy, mainly I-seeded. [Latin, referring to the curved keel of the corolla.]
Leaves firm; bracts large; plant villous-brown-pubescent.
Glycine comosa L. Sp. Pl. 754. 1753. Glycine bracteata L. Sp. Pl. 754. 1753. Glycine monoica L. Sp. Pl. Ed. 2, 1023. 1763. Amphicarpa monoica Ell. Journ. Acad. Phil. 1: 373.
1817. Falcata comosa Kuntze, Rev. Gen. Pl. 182. 1891.
Slender, simple or sparingly branched, climbing, pubescent or glabrate, 1°-8° long. Stipules oblong or ovate, 2" long, striate; leaflets broadly ovate or rhombic-ovate, acute at the apex, rounded at the base, the lower inequilateral, 1'-3' long; racemes of petaliferous flowers mainly simple; bracts small, ovate, obtuse; flowers purplish or white, 6"-7" long; pedicels equalling or exceeding the bracts; pods of the petaliferous flowers about 1' long, 3" wide, pubescent.
Amphicarpaea Pitcheri T. & G. Fl. N. A. I:
292. 1838. F. Pitcheri Kuntze, Rev. Gen. Pl. 182. 1891.
Similar to the preceding but generally stouter, villous-pubescent throughout with reflexed brown hairs. Leaflets larger and thicker, sometimes 4' long; pedicels mostly shorter than the nearly orbicular canescent bracts; ovary and pods of the petaliferous flowers pubescent throughout, subterranean fruit less abundantly produced than in F. comosa; calyx larger.
Moist thickets, Massachusetts to Virginia, New York, South Dakota, Tennessee and Texas. Perhaps a race of the preceding species. Aug.-Sept.