44 KEY TO THE SPECIES 



6. Astragalus liypoglottis L. (Purple Milk-vetch). Low, spreading, 

 branched ; leaflets elliptic ; flowers capitate ; pod membranous, densely white- 

 hairy. 



§ 5. Acaulescent ; leaflets 11-17 ; flowers white or yellowish ; pod densely 

 white-woolly, 1-celled. 



7. Astragalus Purshii Dougl. (Pursh's Milk-vetch). Silvery or white, with 

 dense woolly hairs ; leaflets oblong ; keel purple-tipped ; pod elliptic, 10-14 mm. 

 long. 



§ 6. Erect or ascending ; leaflets 11-31 ; flowers ochroleucus ; pod glabrous, 

 1-celled. 



8. Astragalus Drummondii Dougl. (Dbummond's Milk-vetch). Stout, 

 erect, 3-5 dm. high, woolly pubescent throughout ; leaflets 17-31, oblong ; pod dis- 

 tinctly stipitate, linear, furrowed dorsally, pendent. Frequent on warm sandy 

 slopes. 



9. Astragalus pectinatus (Hook.) Dougl. (Narrow- leaved Milk-vetch). 

 Nearly glabrous, erect or ascending S-4 dm. high ; leaflets 11-19, narrowly linear, 

 2-5 cm. long ; pod terete, sessile, Sandy plains ; common. 



§ 7. Stems tufted, tall ; leaflets 15-25 ; flowers purple ; pod 2-grooved dorsally, 

 at length glabrous. 



10. Astragalus bisulcatus (Hook.) Gray (Two-grooved Milk-vetch). 

 Puberuleut, 3-7 dm. high, mostly in dense clumps ; leaflets oblong ; flowers in long 

 racemes, on peduncles surpassing the leaves; pod stipitate, drooping, membranous. 

 Alkaline plains ; common. 



§ 8. Nearly acaulescent, spreading ; leaflets 7-23 ; flowers blue, violet or purple; 

 pod terete or flattened, 1-celled. 



11. Astragalus Missouriensis Nutt. (Missouri Milk-vetch). Silvery-silky, 

 tufted ; the stems short and prostrate ; leaflets 9-17, oblong or elliptic, 10-12 mm. 

 long ; flowers purple ; pod oblong-lanceolate, coriaceous, transversely rugose, 

 nearly straight ; 2-3 cm. long. Open plains. 



12. Astragalus Shortianus Nutt. (Short's Milk-vetch). Very similar, leaf- 

 lets 9-13, elliptic to broadly obovate ; flowers blue or violet ; pod ovate-lanceolate, 

 strongly curved at apex. When not In fruit may be distinguished from the pre- 

 ceding by the broader, less canescent. thick leaves, the less tufted habit and the 

 deep-blue flowers. Sandy draws and ridges. 



13. Astragalus alpinus L. (Alpine Milk-vetch). Nearly glabrous ; stems 

 spreading-assurgent ; leaflets 11-23, thin, oyal, obtuse, often notched ; flowers from 

 nearly white to violet, on long peduncles ; pod membranous, stipitate, black- 

 pubescent. Stony valleys in the mountains. 



§ 9. Caespitose ; leaflets simple or 3-5-foIiate ; flowers purple ; pod small, 

 1-celled, coriaceous. 



14. Astragalus spatulatus Sheld. (Tufted Milk-vetch). Forming broad, 

 low, densely silvery canescent mats, which become almost hidden by the small 

 crowded purple flowers : leaves simple or 3-5 pinnate, narrowly linear-spatulate, 

 2-4 cm. long ; raceme elongated in fruit ; the pod few-seeded. 



15. Astragalus sericoleucus Gray (Hoary Milk-vetch), Similarly tufted, 

 silky-pubescent ; leaves trifoliate ; the leaflets oblong, 6-12 mm. long ; peduncles 

 few-flowered (2-6) ; pod ovoid, acute. 



