1–6 cm, rachis about equaling longest leaflet; leaflets 7 or 9(–13), congested on rachis, blade surfaces shaggy-pilose. |
basally clustered or cauline, alternate, mostly odd-pinnate; stipules present, sometimes persistent, adnate to petiole, often connate-sheathing; petiolate, petiole sometimes persistent as marcescent thatch on caudex, rarely as pungent spines; leaflets 1–45(–70), usually opposite, subopposite, scattered (irregularly spaced), or fasciculate, rarely alternate or verticillate, usually jointed to rachis, blade margins entire, surfaces usually pubescent, sometimes glabrous. |
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1. Plants usually caulescent (1+ internodes apparent); legumes subsessile or stipitate, pendulous or spreading-declined. | → 2 |
2. Leaflets 11–17, blades broadly lanceolate to oblanceolate, apices acute or subacute; racemes 20–40-flowered; introduced, Idaho, Montana, North Dakota, Utah, Wyoming. | O. riparia |
2. Leaflets (9–)15–41, blades ovate, lanceolate, or lanceolate-oblong, apices acute to obtuse; racemes (2–)4–25[–30+]-flowered; native, widespread in w North America. | O. deflexa |
1. Plants acaulescent or appearing acaulescent (internodes concealed by leaf bases); legumes sessile, subsessile, or stipitate, erect, spreading, or spreading-declined. | → 3 |
3. Legumes spreading-declined. | O. deflexa |
3. Legumes erect or spreading. | → 4 |
4. Base of herb sheathed with reddish, purplish, or purplish brown stipules. | → 5 |
| O. maydelliana |
| → 6 |
6. Racemes 1–3-flowered; legumes stipitate, reclining on ground at maturity, usually at least 3 times longer than wide. | O. kokrinensis |
6. Racemes 5–8-flowered; legumes sessile, held aloft at maturity, to 3 times longer than wide. | O. kobukensis |
4. Base of herb with light tan or grayish stipules, sometimes black in O. campestris). | → 7 |
7. Leaflets usually 1 or 3, rarely 5, decurrent or obscurely articulated with rachis. | O. mertensiana |
7. Leaflets (1–)5–45(–70), jointed to rachis. | → 8 |
8. Plants glandular-viscid (especially stipules and calyces); bracts glabrous, except margins ciliate. | O. borealis |
8. Plants not glandular-viscid; bracts pilose or villous. | → 9 |
9. Racemes usually 1–5-flowered; corollas pink, purple, or bluish, not yellow, ochroleucous, or white (except in white morphs). | → 10 |
10. Corollas (14–)16–22 mm; leaflets 9+, alternate, opposite, subopposite, widely scattered, or fasciculate; stipular margins with clavate processes mixed with cilia. | O. arctica |
10. Corollas 6–20(–24) mm; leaflets 5–17, widely scattered or opposite, not fasciculate; stipular margins ciliate, without clavate processes (except in some O. nigrescens). | → 11 |
11. Legumes erect, usually black-pilose, rarely glabrous or white-pilose; stipules usually prominent, glabrous or sparsely pilose abaxially, stramineous; interior Alaska, Yukon, Northwest Territories, British Columbia. | O. scammaniana |
11. Legumes spreading to ascending, glabrous or pilosulous; stipules not especially conspicuous, pilose, silky-pilose, villous, or glabrous abaxially, whitish to light tan, grayish, or black; widespread. | → 12 |
12. Calyces usually conspicuously swollen or inflated at anthesis, investing legumes or nearly so (if not conspicuously inflated, O. lagopus var. atropurpurea, calyx villous to shaggy-villous); Alberta, Colorado, Idaho, Montana, Nebraska, South Dakota, Utah, Wyoming. | → 13 |
13. Legumes strigose-canescent, leathery, rigid at maturity; Wyoming. | O. nana |
13. Legumes villous, papery, not rigid at maturity; Alberta, Colorado, Idaho, Montana, Nebraska, South Dakota, Utah, Wyoming. | → 14 |
14. Bracts ovate to broadly lanceolate, flat; plants pulvinate-cespitose; Colorado, Nebraska, Utah, Wyoming. | O. multiceps |
14. Bracts ovate-lanceolate to lanceolate, margins involute; plants cespitose but not pulvinate; Alberta, Idaho, Montana, South Dakota, Wyoming. | O. lagopus |
12. Calyces slightly inflated at anthesis, not investing legume at maturity; n Canada to sw United States. | → 15 |
15. Legumes 10–18(–23) mm, sessile or subsessile, glabrous or minutely strigose or strigulose, unilocular; racemes 1 or 2 (or 3)-flowered; Alaska, British Columbia, Yukon. | O. huddelsonii |
15. Legumes (7–)9–38(–40) mm, sessile, subsessile, or stipitate, usually pilose, pilosulous, villous, villous-pilose, hirtellous, strigulose, or strigose-pilosulous, rarely glabrous, unilocular, subunilocular, sub-bilocular, or bilocular; racemes 1–12-flowered; widespread. | → 16 |
16. Legumes ovoid-ellipsoid or bladdery-inflated, stipitate; leaflet blades falcate. | O. podocarpa |
16. Legumes oblong, oblong-ellipsoid, lanceoloid-ovoid, ovoid, or bladdery-inflated, usually sessile, subsessile, or short-stipitate (stipitate in O. nigrescens var. lonchopoda); leaflet blades not falcate. | → 17 |
17. Corollas 12–20 mm; leaflet surfaces usually silky- or silvery-canescent, villous, strigose, or loosely pilose, rarely glabrous; n North America. | O. nigrescens |
17. Corollas usually 6–12.5 mm (to 17 mm in O. oreophila var. jonesii); leaflet surfaces pilose, villous-pilose, or silky-pilose; w United States. | → 18 |
18. Racemes 3–5-flowered; legumes ellipsoid, cylindroid, bladdery-inflated. | O. oreophila |
18. Racemes 1–3 (or 4)-flowered; legumes oblong to lanceoloid-ovoid or ovoid, not bladdery-inflated. | O. parryi |
9. Racemes usually 6–many-flowered; corollas pink, pink-purple, lavender, bluish purple, blue, purple, pinkish violet, if racemes fewer-flowered, then corollas yellow, ochroleucous, or white. | → 19 |
19. Hairs malpighian; corollas usually pink-purple, rarely white. | O. lambertii |
19. Hairs basifixed; corollas pink, pink-purple, lavender, bluish purple, blue, purple, pinkish violet, white, whitish, yellowish, or creamy white. | → 20 |
20. Corollas usually 6–12.5 mm (to 17 mm in var. jonesii); legumes bladdery-inflated; Arizona, California, Nevada, Utah. | O. oreophila |
20. Corollas (10–)12–27(–28) mm; legumes cylindric, subcylindric, ovoid, ovoid-oblong, or ovoid-acuminate, not bladdery-inflated; Canada, w United States, not including Arizona or California. | → 21 |
21. Calyces swollen at anthesis, accrescent and enclosing fruit. | → 22 |
22. Calyces villous to shaggy-villous, hairs mixed blackish and white, appearing gray; legumes villous, papery to nearly membranous; Alberta, Idaho, Montana, South Dakota, Wyoming. | O. lagopus |
22. Calyces densely shaggy-hirsute and subtomentose, hairs white; legumes strigose-canescent, firm; Wyoming. | O. nana |
21. Calyces not or slightly swollen in fruit, usually ruptured by fruit. | → 23 |
23. Corollas white or yellowish. | → 24 |
24. Corollas (10–)12–20(–23) mm; leaflets 7–45; legumes papery to leathery or membranous. | O. campestris |
24. Corollas (14–)16–27(–28) mm; leaflets 7–19(–21); legumes fleshy when fresh, becoming leathery or almost woody and rigid, or thinly papery. | → 25 |
25. Leaflets 7–19(–21), blade surfaces sericeous, often densely so; racemes subcapitate to elongate, 5–20+-flowered; legumes fleshy when fresh, becoming leathery or almost woody and rigid. | O. sericea |
25. Leaflets 11–17, blade surfaces pilose; racemes relatively short to subcapitate, 2–10-flowered; legumes thinly papery. | O. arctica |
23. Corollas pinkish or purplish (rarely creamy white in O. splendens). | → 26 |
26. Calyces with blackish hairs and long, white hairs, appearing gray; leaves 1–10 cm; Alberta, Idaho, Montana, South Dakota, Wyoming. | O. lagopus |
26. Calyces with white hairs, if with both blackish and white, then not from Wyoming or adjacent states; leaves 1.5–28 cm; Alaska east to Newfoundland and Labrador, south to New Mexico. | → 27 |
27. Corollas 17–25 mm; stipules papery or membranous, light tan or pale gray; Colorado, Idaho, Montana, Nevada, Saskatchewan, Utah, Wyoming. | O. besseyi |
27. Corollas 11–22(–23) mm; stipules rigid, fragile, or membranous, purplish, yellowish, or grayish; widespread. | → 28 |
28. Corollas (14–)16–22 mm; stipular margins ciliate, with clavate processes; n, w Alaska, Manitoba, Northwest Territories, Nunavut, Yukon. | → 29 |
29. Stipules firm, usually purplish, usually well separated on elongate caudex branches; leaflets not fasciculate; Kobuk River drainage, Alaska. | O. kobukensis |
29. Stipules fragile, grayish or yellowish, strongly imbricate; leaflets usually fasciculate; Alaska, Manitoba, Northwest Territories, Nunavut, Yukon. | O. arctica |
28. Corollas 11–20(–23) mm; stipular margins ciliate or not, with or without clavate processes; n, nw North America, seldom in arctic. | → 30 |
30. Leaflets fasciculate or not; corollas 11–20(–23) mm, calyces tubes (3.7–)4–9 mm; stipules glabrous, strigose, or pilose abaxially becoming glabrate, with or without marginal clavate processes; Alaska, se, n Yukon, Alberta, n, c British Columbia, North Dakota. | O. campestris |
30. Leaflets usually fasciculate, rarely verticillate; corollas 12–16 mm, calyces tubes 5–6.5 mm; stipules silky-pilose abaxially, without marginal clavate processes; e Alaska, s Yukon, e to Hudson Bay, s to Colorado. | O. splendens |
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