THISTLE FAMILY 



977 



Plant 1-2 dm. (rarely 3 dm.) high; leaves thick, subentire, or with a few teeth; bracts 

 linear-lanceolate. 5. A. pumila. 



III. GRANULIFERAE. 

 One species. 



IV. GRACILES. 

 Upper leaves not linear. 



Bracts Linear-lanceolate; leaves thin, usually more or less dentate. 

 Bracts oblanceolate; leaves thick, usually entire. 

 Upper stem-leaves linear, much reduced. 



6. A. granulifera. 



7. A. gracilis. 



8. A. puberula. 



9. A. arnoglossa. 



10. A. Jonesii. 



V. LATIFOLIAE. 



Leaves decidedly hairy, especially above. 

 Leaves nearly glabrous. 



Achenes slightly glandular-granuliferous, and with a few scattered hairs above. 

 Leaves not saliently toothed, merely denticulate. 11. A. tentorum. 



Leaves saliently and coarsely toothed. 12. A. Hfenziesii. 



Achenes glabrous; leaves more or less toothed. 13. A. lati folia. 



VI. DlVERSIFOLIAE. 



Leaves thin, nearly glabrous. 



Leaves thick, densely glandular-puberulent, at least above. 



14. A. silvatica. 



15. A. diversifolia. 



VII. LONGIFOLIAE. 



Involucre merely puberulent or glandular-granuliferous; leaves not caudate-attenuate; 



stem usually over 3 dm. high. 16. A. longifolia. 



Involucre copiously hirsute, as well as puberulent; leaves caudate-acuminate. 



17. A. caudata. 



VIII. MOLLES. 



Involucre villous, not at all glandular or viscid. 18. A. madlenta. 



Involucre more or less glandular or viscid. 



Involucre densely glandular-granuliferous, only with a few white hairs. 



19. A. arcana. 

 Involucre decidedly villous or hirsute, as well as glandular. 



Middle stem-leaves broadly ovate, less than 5 cm. long; stem 2-3 dm. high. 



Involucre less than 1 cm. high, villous at the base, only slightly glandular; 

 bracts broadly lanceolate. 20. A. coloradensis. 



Involucre 12-15 mm. high, densely glandular-hirsute; bracts narrowly ob- 

 lanceolate. 21. A. ovata. 

 Middle stem-leaves lanceolate, oblanceolate, or Linear-lanceolate. 



Bracts oblanceolate, abruptly acuminate. 22. A. mollis. 



Bracts Linear or lanceolate. 



Stem-leaves more or less sharply dentate, except at the base. 

 Leaves nearly glabrous, except the margins. 



Stem-leaves ovate-lanceolate, broad at the base. 



23. A. amplexifolia. 

 Stem-leaves oblanceolate or narrowly lanceolate, narrowed at the 



base. 24. A. Macounii. 



Leaves decidedly pubescent, both villous and glandular-granuliferous. 



25. A. rivularis. 

 Stem-leaves entire, sparingly denticulate, densely glandular-puberulent. 



26. A. subplumosa* 



IX. FOLIOSAE. 



27. A. tomentulosa* 



Pubescence of the leaves long and soft, villous. 

 Bracts obovate-oblanceolate, mostly obtuse. 

 Bracts oblong-lanceolate, acute. 



Plant sparingly pubescent, with long flat hairs; leaves long-acute. 



28. A. Chamissonis. 

 Plant densely pubescent with fine hairs; leaves acute or obtuse. 



Leaves broadly oblanceolate or lanceolate. 29. A. rhizomata. 



Leaves Linear or lance-linear. 30. A. foliosa. 



Pubescence of the leaves very short and fine. 



Stem-leaves Linear-lanceolate, usually entire or callous-denticulate; involucre rarely 



more than 1 cm. high. 



Pubescence of the involucre and peduncle very short and fine. 31. A. ocreata. 

 Pubescence of the involucre and peduncle longer and coarser. 32. A. celsa. 

 Stem-leaves broadly lanceolate, more or less dentate; involucre usually more than 1 

 cm. high. 33. A. rubricaulis. 



X. ALPIXAE. 



Stem-leaves ovate. 



Stem-leaves Linear to lanceolate. 



Leaves glabrate in age, at least above. 



Involucre and peduncle more or less glandular-puberulent; achenes hispidulous. 



9. A. arnoglossa. 

 Involucre more or less villous, at least at the base; achenes canescent. 



Leaves and lower part of the stem glabrous or nearly so; leaves mostly acute; 



bracts green. 



Leaves strongly 3-ribbed. 34. A. Rydbergii. 



Leaves faintly 3-ribbed. 35. A tennis. 



35 



20. A. coloradensis. 



