4(2). Phyllaries glabrous on the back, sometimes ciliate on the margin (5) 



4. Phyllaries more or less densely glandular or pubescent on the back (10) 



5(4). Plants annual (doubtful cases should be keyed under both alternatives) (6) 



5. Plants perennial (7) 



6(5). Rays exceeding the not very copious pappus; phyllaries all linear or lance- 

 linear, acuminate, with a scarious margin; heads loosely panicled 

 3. A. subulatus. 



6. Rays shorter than the very copious and soft mature pappus; outer phyllaries 



narrowly oblong or linear-spatulate, obtuse or merely acutish, 

 herbaceous; heads usually numerous and crowded. ...5. A. frondosus. 



7(5). Rays white, very rarely lavender 6. A. falcatus. 



I. Rays violet or purple, rarely (in a form of A. foliaceus) white (8) 



8(7). Plants normally tall, 5 dm. tall or more 7. A. hesperius. 



8. Plants normally low (not more than 3 dm. tall) and simple or little-branched; 



outer phyllaries narrowly spatulate to oblong-obovate (9) 



9(8). Outer phyllaries narrowly spatulate, about I mm. wide; leaves normally 



narrow (less than 1 cm. wide), not or scarcely clasping 



8. A. chilensis. 



9. Outer phyllaries broadly oblong-spatulate or oblong-obovate, 2.5-5 mm. wide; 



leaves usually more than 1 cm. wide and definitely clasping 



9. A. foliaceus. 



10(4). Rays white; heads usually numerous and small, not more than 1.5 cm. 

 wide (including the rays); phyllaries never glandular, several seriate, 

 with a whitish coriaceous base and an abrupt usually rhombic 

 green tip, normally cuspidate or mucronate 6. A. falcatus. 



10. Rays lavender or purple; heads usually larger; phyllaries usually glandular 



(11) 



11(10. Leaves grasslike, entire; phyllaries subherbaceous throughout or the inner 

 ones narrowly scarious-niargined; leaves elongate-linear or the lower 

 ones narrowly spatulate; involucre densely stipitate-glandular, with- 

 out other pubescence 10. A. pauciflorus. 



II. Leaves not grasslike, usually toothed; phyllaries not subherbaceous through- 



out (12) 



12(11). Perennial; involucre not conspicuously many-ranked; leaf margins 

 usually hispidulous-ciliate or serrulate 8. A. chilensis. 



12. Biennial; involucre conspicuously many-ranked; phyllaries with a whitish 



chartaceous base and an abrupt often squarrose herbaceous tip 



1 1. A. tephrodes. 



13(1). Distribution in Oklahoma (14) 



13. Distribution in Texas (22) 



14(13). Involucre and parts of herbage glandular 12. A. novae-angliae. 



14. Plants not glandular (15) 



15(14). Phyllaries with the midrib greenish but this greenish area not expanded 

 toward the apex or at the broadest part not more than twice as 

 wide as at the narrowest part, usually appearing linear, the marginal 

 areas pale and chaffy in texture; leaves when present usually sub- 

 ulate, tapered all the way from base to apex, rarely with a few 

 serrations, mostly entire and glabrous; head-bearing branchlets 

 nearly naked (1 6) 



15. Phyllaries usually with a green splotch toward the apex formed by the lateral 



expansion of the greenish area near the midrib; leaves variously 

 ovate to lanceolate or linear but usually serrate, rarely subulate; 

 head-bearing branchlets usually leafy (17) 



1616 



