800 



COMPOSITAE (composite FAMILY^ 



like tips. Receptacle flat, alveolate. Achenes more or less flattened ; pappus 

 simple, of capillary bristles (double in §§ 4 and 5). — Perennial herbs (annual 

 only in §§ 7 and 8), with corymbed, panicled, or racemose heads, flowering 

 chiefly in autumn. Rays white, purple, blue, or pink ; the disk yellow, often 

 changing to purple. Species often without sharply defined limits, freely hybrid- 

 izing. (Name aa-T-qp^ a star, from the radiate heads of flowers. ) 



N.B. — In this genus the heads are drawn on a scale of f, the leaves ^. 



A. At least the basal leaves cordate and definitely petioled B. 

 B. Stem-leaves petioled or sessile, not clasping C. 

 C. Ravs white D. 

 D. Plant not glandular E. 

 E. Heads corj'mbose. 



Involucre ovoid-campanulate, thick-cylindric, or turbinate ; 

 tufted basal leaves few or none. 

 Leaves thin, smoothish, at least not rough above . . 1. A. divaricaius. 

 Leaves thick, rouph above. 



Inflorescence slightly forking ; heads few, 1-1.5 cm. high 3. A.fv/rcatus. 

 Inflorescence much branched; heads numerous, hardly 



1 cm. high ^. A. glomerat/ua. 



Involucre slender, cylindric ; large tufted basal leaves abun- 

 dant Z. A. Sehreberi. 



E. Heads paniculate IZ. A. cordifolius. 



D. Glandular, at least as to the branches of the inflorescence . . 6. A. macrophyllus. 

 C. Rays blue or violet F. 

 F. Plant not glandular O. 



G. Involucral bracts with squrroase tips ; rays many (about 40) . 19. A. anomalua, 

 G. Involucral bracts appressed or a^scending; rays fewer (10-20) IT. 

 H. Leaves entire or essentially so, firm, much longer than wide. 



Leaves harsh above 20. ^. azurem. 



Leaves smooth above 21. A. Shortii. 



H. Leaves serrate, mostly thinner /. 



/. Involucre 4-6 mm. high ; bracts appressed, with conspicu- 

 ous colored tips ; heads abundant, paniculate. 

 Cordate leaves mostly on slender petioles, neither glau- 

 cous nor very smooth 1Z. A. cordifolius. 



Cordate leaves mostly on winged petioles, glaucous be- 

 neath, smooth 2^. A. Lowrieanus. 



J. Involucre 6-10 mm. high ; bracts loose, without conspicu- 

 ously colored tips. 

 Heads abundant, densely racemo-paniculate. 



Stem essentially glabrous 25. A. sagittifollun. 



Stem densely short-pubescent 26. .4. Drummondii. 



Heads fewer, loosely paniculate or subcorymbose . . 27. A. Lindleyanus. 

 F. At least the branches of the inflorescence glandular ... 6. A. macrophyllus. 



B. Stem-leaves mostly cordate-clasping 22. ^. undulatus. 



A. None of the leaves at once cordate and definitely petioled J. 

 J. At least the lower leaves abruptly narrowed or constricted below 

 the middle. 

 Leaves essentially entire, at most slightly constricted above the 



base . 18. j4. patens. 



Leaves sharply serrate, the lower contracted to winged petioles. 



Leaves with abruptly dilated aurlculate-clasping bases . . 48. A. pren anthoides. 



Leaves without dilated bases, scarcely clasping . . . . 47. .4. tardiflorus. 

 J. Leaves not abruptly narrowed or constricted below K. 

 E. Stem-leaves with cordate- or auriculate-clasping bases L. 

 L. Involucre glandular-hairy ; rays usually deep violet M. 

 M. Leaves conspicuously cord ate -clasping, mostly entire. 



Branchlets glandular-viscid ; involucre hemispherical ; bracts 



subequal, linear-attenuate, loose 14. A.novae-angliae. 



Branchlets not glandular ; involucre turbinate ; bracts un- 

 equal, linear-oblong, with slightly spreading green tips . 18. A. patens. 

 M» Leaves obscurely cordate-clasping. 



Plant rigid, freely branching ; leaves mucronate-tipped ; in- 

 volucral bracts unequal, linear or linear-oblong, with 



spreading tips 13. ^. ohlongifolius. 



Plant not rigid, bearing few terminal heads ; leaves thin, 



acuminate ; bracts equal, linear-attenuate . . .15. A. modestus. 

 Z. Involucre not glandular-hairy 7^. 

 _V. Bracts of the involucre distinctly imbrica*-ed, i.e. the outer 

 series successively shorter O. 

 0. Plant smooth and glaucous. 



Leaves lanceolate to ovate ; heads paniculate . . .29. A. laevis. 

 Leaves narrower ; heads solitary or racemose . , . .SO. A. virgatus. 

 O. Plant not glaucous. 



Tips of bracts squarrose or recurved-spreading. 



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