COMPOSITAE. 947 



Heads 25 mm. broad or more; leaves of the branches large, long, lanceolate, acumi- 

 nate. 



Involucral bracts mainly acute; teeth of leaves salient. 3. A. tenebrosus. 

 Involucral bracts, all but the lowe;ft, obtuse; leaves low-serrate, the teeth chiefly 

 appressed. 4. A. leptocaulis. 



(b) Leaves thick, firm, rough, at least when dry. 



Heads 12-16 mm. high; inflorescence forking. 5. A.furcatus. 



Heads 8-10 mm. high ; inflorescence paniculate or glomerate. 



Leaves acute, or short-acuminate, pilose beneath; inflorescence glomerate. 



6. A. glomeratus. 

 Leaves long-acuminate, not pilose beneath ; inflorescence open-paniculate. 



7. A. Clay t on i. 



f f Involucre cylindric, its bracts tapering to an obtuse apex ; basal leaves large, tufted. 

 Bracts of the involucre pale, scarious, usually without herbaceous tips. 



8. A. curvescens. 

 Bracts of the involucre broader, with herbaceous tips. 9. A. Schreberi. 



Rays violet, usually 3-toothed ; plants glandular. 

 t Predominant glands large, capitate; leaves thick, coarse, heavy. 

 Sinus broad; glands chiefly on the inflorescence; plant usually harsh. 



10. A. macrophyllus. 

 Sinus narrow; glands abundant on the leaves and stem; growing plant clammy. 



11. A. roscidus. 

 \ \ Predominant glands minute, scarcely capitate; leaves usually thin. 



(a) Inflorescence rather regular, flat, or convex-topped ; plants usually less than 8 dm. tall. 

 Sinus broad, shallow. 



Broader leaves orbicular-cordate, their teeth and the inflorescence-leaves inconspicu- 

 ous. 12. A. ianthinus. 

 Broader leaves reniform, sharply incised; some inflorescence-leaves conspicuous. 



13. A. violaris. 

 Sinus rather deep and narrow; broader leaves ovate-cordate, sharply serrate. 



14. A. imiltiformis. 



(b) Inflorescence very irregular, paniculate-corymbose; plants often 1.2-1.6 m. high; 



broader leaves large, cordate, acute. 15. A. nobilis. 



* * Rays blue or purple; plants not glandular. 



t Bracts of the involucre spreading or recurved ; rays 30-45. 



16. A. anomalus. 

 \ t Bracts of the involucre appressed, or erect; rays 8-20. 



(a) Leaves all entire, or nearly so, thick, or firm. 



Leaves nearly or quite glabrous above. 17. A. Shortii. 



Leaves rough-puberulent on both sides, the upper bract-like. 18. A. azureus. 



(b) Leaves nearly all sharply serrate, thin. 

 Heads 4-6 mm. high, numerous; bracts obtuse or obtusish. 



Leaves rough; petioles not wing-margined; bracts appressed. 



19. A. cordifolius. 

 Leaves smooth, or nearly so ; petioles, or some of them, wing-margined. 



20. A. Lowrieanus. 



Heads 8-10 mm. high, usually few ; bracts acute or acuminate. 21. A. Lindleyanus* 

 Heads 6-10 mm. high, numerous; bracts acute or acuminate. 



Stem densely and finely pubescent. 22. A. Drummondii. 

 Stem glabrous or nearly so ; bract-tips spreading. 



Inflorescence racemose-paniculate. 23. A. sagittifolius. 



Inflorescence corymbose-paniculate. 24. A. Saundersii. 



2, Stem-leaves, or some of them, cordate-clasping; plant rough when dry. 



25. A. undulatus. 



B. Ko cordate and petioled leaves; those of the stem, or some of them, with more or 



less cordate or anricled clasping bases. 



i. Stem rough, or hirsute-pubescent. 



* Leaves entire, oblong, linear, or lanceolate. 



Heads 2.5-5 cm - broad ; leaves sessile, strongly cordate- clasping. 



f Stem rough ; leaves oblong to lanceolate; involucre turbinate. 

 Leaves thick, firm, very rough, oblong to oval. 26. A. patens. 



Leaves thin, roughish, oblong-lanceolate. 27. A.phlogifolius. 



t t Stem hirsute; leaves lanceolate ; involucre hemispheric. 



28. A. Novae-Angliae. 



% Heads 1-2.5 cm - broad ; leaves but slightly clasping. 



Involucre hemispheric, its bracts glandular. 29. A. oblongifolius, 



Involucre turbinate, its bracts hispidt 30, A, amethystinus. 



