1. P. Onóbrychis, Nutt. Nearly smooth and free from glands, erect (3–5° high); leaflets lanceolate-ovate, taper-pointed (3´ long); stipules and bracts awl-shaped; racemes elongated; peduncle shorter than the leaves; pods roughened and wrinkled.—River-banks, Ohio to Ill. and Mo.; also south and east to S. C. July.
2. P. stipulàta, Torr. & Gray. Nearly smooth and glandless; stems diffuse; leaflets ovate-elliptical, reticulated; stipules ovate; flowers in heads on rather short peduncles; bracts broadly ovate, sharp-pointed.—Rocks, S. Ind. and Ky. June, July.
3. P. melilotoìdes, Michx. Somewhat pubescent, more or less glandular; stems erect (1–2° high), slender; leaflets lanceolate or narrowly oblong; spikes oblong, long-peduncled; stipules awl-shaped; bracts ovate or lanceolate, taper-pointed; pods strongly wrinkled transversely.—Dry soil, Fla. to Tenn., S. Ind. and Kan. June.
[*][*] Leaves palmately 3–5-foliolate; roots not tuberous.
4. P. tenuiflòra, Pursh. Slender, erect, much branched and bushy (2–4° high), minutely hoary-pubescent when young; leaflets varying from linear to obovate-oblong (½–1½´ long), glandular-dotted; flowers (2–3´´ long) in loose racemes; lobes of the calyx and bracts ovate, acute; pod glandular. (P. floribunda, Nutt.)—Prairies, Minn. to Ill., Tex., and westward. June–Sept.
5. P. argophýlla, Pursh. Silvery silky-white all over, erect, divergently branched (1–3° high); leaflets elliptical-lanceolate; spikes interrupted; lobes of the calyx and bracts lanceolate.—High plains, N. Wisc. to Iowa, Kan., and westward. June.—Flowers 4–5´´ long.
6. P. digitàta, Nutt. More slender and less hoary, 1–2° high; leaflets linear-oblanceolate; bracts of the interrupted spike obcordate; calyx-lobes oblong, acute.—Central Kan. to Col. and Tex.
7. P. lanceolàta, Pursh. Glabrous or nearly so, yellowish green, densely punctate; leaflets 3, linear to oblanceolate; flowers small, in very short spikes; calyx 1´´ long, with short broad teeth.—Central Kan. to the Sask. and westward.
[*][*][*] Leaves palmately 5-foliolate; root tuberous; spike-like racemes dense.
8. P. esculénta, Pursh. Roughish hairy all over; stem stout (5–15´ high) and erect from a tuberous or turnip-shaped farinaceous root; leaflets obovate- or lanceolate-oblong; spikes oblong, long-peduncled; lobes of the calyx and bracts lanceolate, nearly equalling the corolla (½´ long).—High plains, Sask. to Wisc., Iowa, and Tex. June. The Pomme blanche, or Pomme de Prairie, of the voyageurs.