FLOWERING PLANTS AND FERNS OF ARIZONA 917 



4. Stems taller, rarely from a branched caudex; leaves (except in A. iniricaius, 

 A. spinosus, and A. riparius) much larger (6). 

 6. Upper leaves tiny, scalelike, entire: stems suffrutescent (except in A. 

 ri pari us, this annual': plants tall 'except in A. Hparius), essentially 

 glabrous; heads medium-sized (7). 

 7. Heads discoid; stems intricately branched; achenes silky. 



11. A. ENTKICATUS. 



7. Heads radiate (8). 



8. Rays purple; plant annual, not spiny; achenes pubescent. 



10. A. RIPARIUS. 



8. Rays white: plant perennial, often spiny: achenes glabrous. 



12. A. spinosus. 

 6. Upper leaves not tiny and scalelike: stems strictly herbaceous or, if 

 somewhat woody (A. abatus), then the heads very large (9). 

 9. Leaves spiny-toothed: heads very large, about 5 cm. wide or more; 



involucre 1.5 to 2.5 cm. high 13. A. abatus. 



9. Leaves not spiny-toothed; heads smaller: involucre much shorter (10). 

 10. Phvllaries glabrous on the back, sometimes ciliate on the margin (11). 

 11. Plants annual (12). 



12. Rays exceeding the not very copious pappus: phvllaries all 

 linear or lance-linear, acuminate, with a scarious margin: 

 heads loosely panicled 14. A. exilis. 



12. Rays shorter than the very copious and soft mature pappus: 



outer phvllaries narrowly oblong or linear-spatulate, obtuse 

 or merely acutish, herbaceous; heads usually numerous and 



crowded 15. A. frondostts. 



11. Plants perennial (13). 



13. Rays white (14). 



14. Plant hairy, not from slender running rootstocks: stem leaves 

 nearly uniform, linear, those of the branches bracteiform: 

 heads numerous: phvllaries with a whitish chartaceous 

 base and an abrupt green tip 2. A. commtjtattts. 



14. Plant glabrous, from slender running rootstocks: lower leaves 



spatulate or oblanceolate, the upper ones linear, all entire; 

 heads solitary or few: phvllaries lanceolate or lance-linear, 

 with a green midline (at least above) and a scarious 



margin 6. A. lemmoni. 



13. Rays violet or purple rarely (in a form of .4. foliaceus) white (15). 

 The typical form of 7. .4. glaucodes received too late to 

 permit remaking the key, would be sought here.) 



15. Plants normally tall (50 cm. high or more) and much branched: 



outer phvllaries linear or lance-linear. 



4. A. COEKTJL.ESCENS. 



15. Plants normally low (not more than 30 cm. high) and simple 



or little branched: outer phvllaries narrowly spatulate to 



oblong-obovate (16). 



16. Outer phvllaries narrowly spatulate, about 1 mm. wide: 



leaves normally narrow (less than 1 cm. wide\ 



not or scarcely clasping 3. A. adscendens. 



16. Outer phvllaries broadly oblong-spatulate or oblong- 

 obovate, 2.5 to 5 mm. wide: leaves usually more than 

 1 cm. wide and definitely clasping. 5. A. foliaceus. 

 10. Phvllaries more or less densely glandular or pubescent on the 

 back (17). 

 17. Rays white: heads usually numerous and small, not more than 

 1.5 cm. wide, including the rays: phvllaries several-seriate, 

 with a whitish coriaceous base and an abrupt, usually rhombic, 

 green tip, normally cuspidate or mucronate, never glandular. 



2. A. COMMUTATUS. 



17. Rays lavender or purple: heads usually larger: phyllaries usually 



glandular (18). 



18. Leaves grasslike, entire, elongate-linear or the lower leaves 



narrowly spatulate; involucre densely stipitate-glandular 



(without other pubescence), the phyllaries subherbaceous 



throughout or the inner ones with narrow scarious margins. 



1. A. PAUCIFLORXJS. 



18. Leaves not grasslike, usually toothed: phyllaries not sub- 

 herbaceous throughout (19). 



