CARDUACEAE. 353 



VI. MULTIFLORI. 



Pubescence of the stem spreading or reflexed. 



Heads less than 5 mm. high. 14. A. exiguus. 



Heads 68 mm. high. 15. A. crassulus. 



Pubescence of the stem appressed or ascending. 



Bracts very unequal in length, well imbricated, the outer much shorter. 

 Bracts narrowly oblanceolate, acutish, especially the inner. 



1 6. A. multiflorus. 

 Bracts broadly oblanceolate or the outer spatulate, very obtuse. 



17. A. polycephalus. 

 Bracts almost equal in length or the outer sometimes longer ; heads few or 



solitary at the ends of the branches. 

 Bracts thick, very squarrose ; leaves thick, densely strigose. 



1 8. A. commutatus. 

 Bracts thin, not squarrose ; leaves sparingly strigose, in age often glabrate. 



19. A. falcatus. 

 VII. SAGITTIFOLII. 



One species. 20. A. Lindleyanus. 



VIII. LAEVES. 



Green tips of the bracts broadly rhombic ; leaves of the branches much reduced. 



21. A. laevis. 



Green tips of the bracts narrowly rhombic or rhombic-oblanceolate ; leaves of 

 the branches gradually but not conspicuously reduced. 22. A. Geyeri. 



IX. PORTERIANI. 



One species. 23. A. Porteri. 



X. SUBRACEMOSI. 



Inflorescence falsely racemose ; leaves linear to oblanceolate. 



24. A. subracemosus. 

 XI. SALICIFOLII. 



Inflorescence elongated, not flat-topped. 



Heads numerous in a much branched panicle ; bracts not with white mid-ribs. 

 Leaves distinctly toothed. 



Disk of the head about i cm. high and broad; leaves thickish. 



25. A. salicifolius. 

 Disk 6-8 mm. high and broad; leaves thin. 26. A. paniculatus. 



Leaves entire, rarely denticulate. 



All bracts narrowly linear ; branches ascending ; rays purplish. 

 Bracts almost linear-filiform, more or less squarrous. 



27. A. hesperius. 



Bracts linear, erect. 28. A. coerulescens. 



Outer bracts broader than the inner, oblanceolate ; branches more di- 

 vergent. 



Rays usually white. 29. A. Osterhoutii. 



Rays purple. 30. A. fluviatilis. 



Heads fewer; bracts with white mid-ribs. 31. A. laetevirens. 



Inflorescence more or less flat-topped. 



Leaves lanceolate to linear-lanceolate, firm ; heads numerous. 



32. A. corymbiformis. 

 Leaves narrowly linear, thin ; heads few. 33. A. longulus. 



XII. LONCHOPHYLLI. 



One species. 34. A. lonchophyllus. 



XIII. OCCIDENTALES. 



One species. 35. A. Fremontii. 



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