800 



COMPOSITAE (composite FAMILY^ 



like tips. Receptacle flat, alveolate. Achenes more or loss 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. Kays white, purple, blue, or pink ; the disk yellow, often 

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

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



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



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

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

 C. Kays white D. 

 D. Plant not glandular E. 

 E. Heads cor}'mbose. 



Involucre ovoid-cam pan ulate, thick-cylindric, or turbinate; 

 tufted basal leaves few or none. 

 Leaves thin, smoothish, at least not rough above 

 Leaves thick, rough above. 



Inflorescence slightly forking ; heads few, 1-1.5 cm. high 

 Inflorescence much branched ; heads numerous, hardly 

 1 cm. high 

 Involucre slender, cylindric ; large tufted basal leaves abun 



QAIiL •■••••••■• 



E. Heads paniculate 



Z>. Glandular, at least as to the branches of the inflorescence . 

 C. Rays blue or violet F. 

 F. Plant not glandular G. 



G. Involucral bracts with squrroase tips ; rays many (about 40) . 



G. Involucral bracts appressed or ascending; rays fewer (10-20) H, 



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



Leaves harsh above 



Leaves smooth above 



H. Leaves serrate, mostly thinner I. 



I. 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 



Cordate leaves mostly on winged petioles, glaucous be- 

 neath, smooth . 



/. Involucre G-10 mm. high ; bi-acts loose, without conspicu- 

 ously colored tips. 

 Heads abundant, densely racemo-paniculate. 

 Stem essentially glabrous , , . . 

 Stem densely short-pubescent 

 Heads fewer, loosely i)aniculate or subcorymbose 

 F. At least the branches of the inflorescence glandular 



B. Stem-leaves mostly cordate-clasping 



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 ... 



Leaves sharply serrate, the lower contracted to ^vinged petioles. 

 Leaves with abruptly dilated auriculate-clasping bases 

 Leaves without dilated bases, scarcely clasping .... 

 J. Leaves not abruptly narrowed or constricted below K. 

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

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

 M. Leaves conspicuously cordate-clasping, mostly entire. 



Branchlets glandular-viscid ; involucre hemispherical ; bracts 



subequal, linear-attoimate, loose 



Branchlets not glandular; involucre turbinate; bracts un- 

 equal, linear-oblong, with slightly spreading green tips . 

 M. Leaves obscurely cordate-clasping. 



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

 volucral bracts unequal, linear or linear-oblong, with 

 spreading tips 



2. A. divaricatus. 



3. A.furcaius. 



4. A. glomeratus. 



5. A. Schreberi. 

 23. A. cordifolius. 



6. A. macrophyllua. 



19. A. anomalus. 



20, A. azuren-8. 



21. A. Shortii. 



23. A. cordifolius. 



24. A. Loxorieanus. 



25. A. sagittifolius. 



26. A. Druiiimondii. 



27. A. Lindleyanus. 

 6. A. macrophyilus. 



22, A. undulatuts. 



18. A. patens. 



48. A.prenanthoides. 

 47. A. tardiflorus. 



14. A.novae-angliae. 

 18. A. patens. 



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

 acuminate ; bracts equal, linear-attenuate 

 L. Involucre not glandular-hairy N. 

 X. Uracts of the involucre distinctly imbricated, i.e. the outer 

 series successively shorter O. 

 (>. Plant smooth and glaucous. 



Loaves lanceolate to ovate ; heads paniculate 

 Leaves narrower ; heads solitary or racemose 

 O. Plant not glaucous. 



Tips of bracts squarrose or recurved-spreading. 



13. A. ohlongifolius. 

 15, A. modestUrS. 



29. A. laevis. 



30. A. virgatus. 



