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Key to Astragalus

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1 Hairs of the stems and leaves malpighian (with 2 arms) (use 10× or greater magnification).
..2 Plants erect or ascending, the stems 3.5-16 dm long; legume 4.0-5.2 mm in diameter; legume (9-) 10-15 mm long; stipules connate, 3-18 mm long; [widespread in our region]; [section Uliginosi]
..2 Plants prostrate or decumbent, the stems to 1.7 dm long; legume (4-) 5-10 mm in diameter; legume 12-37 mm long; stipules not connate (or rarely so towards the base of the plant only), (2-) 3-9 mm long; [OK and TX westwards].
....3 Calyx tube 3.2-4.5 mm long; keel petal 4.2-9.8 mm long; corollas whitish, ochroleucous or pink to lavender (usually only lightly so); [section Lotiflori]
....3 Calyx tube 6.3--9.3 mm long; keel petal (11.5-) 12.8-17.3 (-18.5) mm long; corollas usually deeply pink or lavender (rarely to whitish); [section Argophylli]
1 Hairs of the stems and leaves basifixed, simple.
......4 Legume pilose with hairs > 1 mm long; stems conspicuously pubescent, the hairs spreading and simple; plants decumbent, spreading, or ascending, the stems 0.5-4 dm long.
........5 Corolla 14-19 mm long; leaflets 17-29; legume bilocular; calyx lobes shorter than the calyx tube; [of calcareous habitats of the interior]
........5 Corolla 8-12 mm long; leaflets (5-) 7-15; legume unilocular; calyx lobes equaling or longer than the calyx tube [of dry sandy habitats from SC south]
......4 Legume glabrous; stems glabrous or inconspicuously pubescent, the hairs appressed, simple or dolabriform; plants erect with stems (3-) 4-15 dm long, or decumbent with stems 1-3 dm long (A. distortus var. distortus and A. bibullatus).
..........6 Plants erect, stems (3-) 4-15 dm long; legume straight to moderately curved.
............ 7 Leaves with 21-31 coriaceous to somewhat fleshy leaflets, many of the leaflets alternate or subopposite; legumes 2-3 cm long, 4-6 mm in diameter; [of dry sandy habitats from NC south]
............ 7 Leaves with 11-23 thin-textured leaflets, all of the leaflets usually opposite; legumes 1.5-2 cm long, 8-18 mm in diameter; [of rocky calcareous habitats from VA north]
..........6 Plants decumbent or ascending, stems 1-5 dm long; legume either dry and strongly curved (about 90 degrees), or globose and initially fleshy.
............ ..8 Legume globose, 1.3-2 cm in diameter, initially fleshy; corolla 18-25 mm long; [of calcareous glades of c. TN]
............ ....9 Pubescence of the calyx densely and softly white-tomentose; flowers yellowish-white; [prairies; s. IL s. to c. LA westward]
............ ....9 Pubescence of the calyx thinly pilose; flowers purple-colored; [endemic to calcareous glades of c. TN]
............ ..8 Legume lanceolate, 1.2-2.5 cm long, 4-7 mm wide, strongly curved; corolla 4-15 mm long; [of various dry habitats, either from w. VA northward or from FL west in the Coastal Plain beyond our area].
............ ......10 Corolla (7-) 8-15 mm long; legume 4-7 mm wide.
............ ........11 Leaflets mostly 1-2× as long as wide, typically noticeably notched at the tip; mature legume reticulately textured; corolla (7-) 8-11 mm long; [of dry sandy sites in FL and possibly adjacent GA and s. MS]
............ ........11 Leaflets mostly 2-3.5× as long as wide, truncate or shallowly notched at the tip; mature legume lacking a reticulately textured surface; corolla 9-15 mm long; [either of shaley habitats from w. VA northward or of woodlands and prairies from MS westward]
............ ..........12 Keel 7-9.5 mm long; legume usually 3-4× as ling as wide, often curved 90°, grooved along sutures on both sides
............ ..........12 Keel 6-7 mm long; legume usually 2.5-3.5x as long as wide, nearly straight or curved < 90°, grooved only along one suture
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