THISTLE FAMILY 251 



Plant acaulescent; heads subsessile among the rosettes of the basal leaves. 

 „, - VIII. ROSULATAE. 



Plants not surculose-j)roliferous; stolons erect. 



Heads 4^5 mm. high; bracts nearly glabrous, scarious throughout; leaves silky- 



tomentose. IX. Argentbae. 



Heads 6-10 mm. high r bracts tomentose at the base, only tips scarious; leaves 

 villous-tomentose. X. Pulcherrimae. 



Pappus-bristles of the small staminate heads not clavate; achenes puberulent; hairs 

 ' bifurcate at the apex; plant low and densely cespitose. XI. Dimorphae. 



I. Kacemosae. 

 Leaves of the rosettes oval or spatulate; lower pedicels 2-5 cm. long. 



1. A. racemosa. 

 Leaves of the rosettes oblanceolate; lower pedicels 1 cm. long or less. 



2. A. oblancifoUa. 

 II. Alpinae. 



Leaves glabrous above. 



Leaves of the rosettes narrowly oblanceolate; heads usually several; bracts of the- 



pistlllate heads abruptly acuminate. 3. A. alpina. 



Leaves of the rosettes broadly oblanceolate or spatulate; inner bracts acute or acum- 

 inate, the outer obtuse. 

 Heads usually solitary. 4. A. monocephala. 



Heads 3-6 in a cluster. 5. A. chlorantha. 



Leaves tomentose on both sides ; bracts acute or obtuse. 



Leaves of the rosett&s broadly obovate-cuneate, subsessile. 



Heads 7-S mm. high; leaves 8-10 mm. long; tips of bracts dark brown. 



6. A. pulvinata. 

 Heads 5-6 mm. high; leaves less than 8 mm. long; tips of the bracts light brown. 



7. A. albescens. 

 Leaves of the rosettes spatulate or oblanceolate, distinctly petioled. 



Heads 6-8 mm. high. 8. A. fusca. 



Heads 5-6 mm. high. 



Bracts very dark, almost black at the base, but often with white tips. 

 Inner bracts of the pistillate heads acute. 



Leaves narrowly oblanceolate, acute or short-acuminate; tomentum 



very fine and appressed. 9. A. acuta. 



Leaves spatulate or broadly oblanceolate, obtuse; tomentum rather 

 loose. 10. A. media. 



Bracts obtuse or rounded. 11. A. mucronata. 



Bracts moderately dark, umber-colored to light brown. 

 Inner bracts not rose-colored. 



Leaves appressed-toineutose, shining and yellowish. 

 Bracts of the pistillate heads linear-lanceolate, acute. 



12. A. Sansoni. 

 Bracts of the heads oblong, obtuse. 



Heads sessile; stolons decumbent. 13. A. flavescens. 



Heads peduncled; stolons ascending. 14. A. conftnis. 



Leaves wjute-tomentose, very rarely yellowish. 

 Heads 2 or 3; leaves broadly obovate-spatulate. 



15. A. aizoides. 

 Heads several ; leaves spatulate or oblanceolate. 



Bracts of the pistillate heads obtuse. 



Involucres more or less viscid; bracts with whitish tips. 



23. A. sedoides. 

 Involucres not viscid ; bracts umber-colored. 



16. A. umhrinella. 

 Bracts of the pistUlate heads acute. 17. A. Macounii. 



Inner bracts rose-colored. 18. A. concinna. 



III. ROSEAE. 

 Leaves cuneate-spatulate, obtuse, without distinction between blade and petiole. 



18. A. concinna. 

 Leaves oblanceolate or spatulate, with distinct petioles. 



Leaves narrowly oblanceolate, acute. 197 A. rosea. 



Leaves broadly spatulate, obtuse. 20. A. imbricata. 



IV. Nardinae. 

 One species. 21. A. corymbosa. 



V. Aridae. 



Stem-leaves 6-8 mm. wide, oblong or the uppermost lanceolate. 22. A. foliacea. 

 Stem-leaves 2-5 mm. wide, linear or oblanceolate. 



Bracts with a large "brown or green spot, more or less viscid. 23. A. sedoides. 

 Bracts slightly if at all spotted, not viscid. 



Bracts of the pistillate heads obtuse; plant 1-2 dm. high. 



Bracts of the pistillate heads with oblong to linear upper portions. 



24. A. arida. 

 Bracts of the pistillate heads with oval or obovate upper portions. 



25. A. scariosa. 

 Bracts of the pistillate heads acute, at least the inner ones. 



Inflorescence and upper leaves glandular-hairy; leaves of the inflorescence 

 large, scarcely smaller than the upper stem-leaves; bracts greenish. 

 Leaves of the stolons 5-15 mm. long, rhombic-spatulate; tomentum very 

 fine, appressed and silky. 28. A. mlcrophylla. 



