compositae. 947 



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

 nate. 



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

 Involucral bracts, all but the lowest, 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. Claytoni. 



\ t 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, 

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

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



10. A. tnacrophyllus. 

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



11. A. roscidus. 

 \ f 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. multiformis. 



(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. 



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



16. A. anoma/us. 

 + 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. Low rie an us. 

 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 0/ them, cordate-clasping ; plant rough when dry. 



25. A. undulatus. 



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



less cordate or auricled clasping bases. 



1. Stem rough, or hirsute-pubescent. 



* Leaves entire, oblong, linear, or lanceolate. 



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

 + 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. 



i t Stem hirsute; leaves lanceolate; involucre hemispheric. 



28. A. Novae-Angliae. 

 I leads 1-2.5 cm - broad ; leaves but slightly clasping. 

 Involucre hemispheric, its bracts glandular. 29. A. oblongi/olius. 



Involucre turbinate, its bracts hispid, 39. A. amethystinus, 



