WOOTON AND STANDLEY FLORA OF NEW MEXICO. 735 



KEY TO THE SPECIES. 



Annuals or biennials. 



Divisions of the leaves lanceolate or linear, incised or pin- 



natifid 1. A. biennis. 



Divisions of the leaves linear-filiform, entire 2. A. caudata. 



Perennials. 



Heads homogamous, i. e., all the flowers fertile. 



All the leaves entire, linear to nan-owly oblong 3. A. cana. 



Most, or at least part, of the leaves 3-toothed at the apex. 

 Bracts of the involucre nearly glabrous, resinous; 



inflorescence lax, racemose 4. A. nova. 



Bracts tomentose; inflorescence not racemose. 



Heads campanulate, recurved 5. A. petrophila. 



Heads tm-binate, erect. 



Tall slarub ; inflorescence much branched . 6. A. tridentata. 

 Low shrub, 40 cm. high or less; inflores- 

 cence rather simple and spikelike.. 7. A. arbuscula. 

 Heads heterogamous, i. e., the flowers unlike, the marginal 

 ones pistillate, the central ones perfect though 

 sometimes sterile by the abortion of the pistil. 

 Central flowers sterile, the style mostly entire and the 

 ovary abortive. 



Plants slirubby, white-tomentose 8. A. filifolia. 



Plants herbaceous except at the very base, green- 

 ish, though sometimes pubescent. 

 Upper leaves all linear, only the basal ones 

 pinnatifid; plants pubescent or glabrous. 



Plants glabrous throughout 9. A. dracunculoides. 



Plants sparingly villous on stems and 



leaves 10. A. dracunculina. 



All the leaves pinnatifid; plants somewhat 

 pubescent. 

 Stems tall, 50 to 100 cm. liigh, very leafy, 

 in age nearly glabrous; divisions of 

 the leaves linear-filiform; pubes- 

 cence scanty 11. A. scouleriana. 



Stems lower, 20 to 60 cm. high; divisions 

 of the basal leaves linear-oblanceo- 

 late, more or less canescently vil- 

 lous 12. A. forwoodii. 



Central flowers fertile; style 2-cleft. 



Receptacle densely woolly with long hairs. 



Heads large, 6 to 12 mm. in diameter; bracts 

 with dark brown or blackish margins; 

 plants low, 10 to 20 cm. high; spikes 



scapose; of alpine meadows 13. A. scopulorum. 



Heads small, 4 to 5 mm. in diameter; bracts 

 light brown; plants taller, 30 to 60 cm. 

 liigh; inflorescence paniculate; of the 



low plains 14. A.frigida. 



Receptacle not woolly, mostly smooth. 



Slirub, 30 cm. high or less; leaves cuneate, 



tridental 3, silky- villous 15. A. bigelovii. 



