COMPOSITAE 



607 



Leaves silky, silvery, or canescent on both sides. 

 Leaves not silky, silvery or canescent. 



Rays normally purple, blue, pink or violet, not 

 white. 

 Tips of the involucral bracts strongly 

 squarrose. 

 Involucre hemispheric or nearly so; 



heads 2.5 cm. broad or more. 

 Involucre turbinate; heads 12-18 

 mm. broad. 

 Tips of the involucral bracts appressed or 

 erect (except in forms of No. 25). 

 Bracts of the involucre coriaceous 

 or herbaceous, not linear-sub- 

 ulate. 

 Bracts of the involucre cori- 

 aceous, obtuse. 

 Bracts of the involucre herb- 

 aceous, acute. 

 Bracts of the involucre linear-subu- 

 late, membranous, acute. 

 Ray essentially white (sometimes pink or 

 purplish in 27, 28, 29, 30 and 35). 

 Heads in a terminal corymb. 

 Heads solitary at the ends of slender 

 branchlets and often disposed in 

 racemes or panicles. 

 Heads scattered, the peduncles pro- 

 longed, scaly. 

 Heads decidedly racemose or panicu- 

 late, the peduncles not scaly. 

 Plants glabrous or pubescent but 

 not harsh. 

 Heads paniculate, not in 1- 

 sided racemes. 

 Blades of the stem 

 leaves of a lan- 

 ceolate or nar- 

 rowly o b lo n g 

 type. 

 Heads mostly 

 over 16 mm. 

 broad. 

 Ray- flowers 

 usually blu- 

 ish violet; 

 leaves firm. 

 Ray-flowers 

 usually 

 w h i t e ; 

 leaves thin- 

 nish. 



23. A. concolor. 



24. A. spectabilis. 



25. A. gracilis. 



26. A. Radula. 



27. A. Herveyi. 



28. A. nemoralis. 



29. A. acuminalus. 



30. A. dumosus. 



31. A. salicif alius. 



32. A. paniculatus. 



