FLOWERING PLANTS AND FERNS OF ARIZONA 879 



6. Rays not sessile and persistent on the achenes (8). 

 8. Leaves opposite (9). 



9. Ray achenes tightly and completely enclosed by the subtending pales. 



40. Melampodium. 

 9. Rav achenes not tightlv and completely enclosed bv the subtending 

 pales (10). 

 10. Rays 1 to 5; leaves roundish-ovate; anthers green. 



39. Guardiola. 

 10. Rays very numerous, small; leaves lanceolate; anthers blackish. 



55. Eclipta. 

 8. Leaves alternate (11 s ). 



11. Heads very small, numerous, in dense flattish or rounded cymose 



panicles 107. Achillea. 



11. Heads relatively large, solitary or few (12). 



12. Receptacle conic, bearing stiff narrow acuminate pales above, 



naked below 106. Anthemis. 



12. Receptacle convex, with broad blunt membranous pales through- 

 out 107a. Leucamptx. 



1. Rays yellow, sometimes partly purple or maroon (13). 

 13. Receptacle not chaffy (14). 



14. Phyllaries graduated in several unequal series, closely imbricate (15). 

 15. Rays 9 or fewer; heads small, very numerous, in dense rounded terminal 



clusters; involucre ovoid or oblong 8. Selloa. 



15. Rays 12 or more: heads relatively large and few, scattered at the ends 

 of the branchlets: involucre campanulate or hemispheric (16). 

 16. Leaves entire; phyllaries with narrow herbaceous tips. 



9. Xaxthocephalum. 

 16. Leaves pinnately dissected; phyllaries with broad scarious tips. 



109. Chrysaxthemum. 

 14. Phyllaries in 1 or 2 series or, if pluriseriate, not graduated in length (17). 

 17. Phyllaries of the outer series about 4, united to the middle or higher 

 into a cup; heads small, numerous, in terminal cymose panicles. 



101. Plummera. 

 17. Phyllaries separate or essentially so (18). 



18. Heads 1- or 2-flowered, in dense glomerate clusters, these sessile in 

 the forks of the stem, or terminal and leafy-involucrate. 



87. Flaveria. 

 18. Heads several- to manv-fiowered, solitarv on terminal peduncles (19). 

 19. Plants woolly (20)/ 



20. Rays persistent, becoming papery 82. Baileya. 



20. Ravs not persistent 93. Eriophyllum. 



19. Plants not woolly (21). 



21. Involucre and leaves with translucent oil glands_ 105. Pectis. 

 21. Involucre and leaves not with translucent oil glands (22). 



22. Leaves linear, entire: receptacle conic 86. Baeria. 



22. Leaves broad, dissected; receptacle fiat 96. Bahia. 



13. Receptacle chaffy, at least toward the margin (23). 



23. Rays pistillate and fertile: disk flowers hermaphrodite but sterile, with 

 a nearly or quite undivided style and an abortive ovary (24). 

 24. Leaves with spinescent lobes and tip, alternate; heads involucrate by 



spinescent bracts 79. Hemizoxia. 



24. Leaves not with spinescent lobes or tip; heads not involucrate by 

 spinescent bracts (25). 

 25. Ray achenes closely and completely enwrapped by the subtending 



phyllaries; leaves opposite 40. Melampodium. 



25. Ray achenes not enwrapped by the subtending phyllaries, but falling 

 in connection with them and with the pales of the opposed outer 



disk flowers; leaves alternate 41. Berlaxdiera. 



23. Rays and disk flowers all fertile (26). 



26. Rays sessile and persistent on their achenes, becoming papery (27 . 

 27. Achenes verv stronglv flattened; phvllaries drv, stronglv graduated. 



52. Zinnia. 

 27. Achenes plump: phyllaries herbaceous at tip, scarcely or not gradu- 

 ated 54. Heliopsis. 



-s(j744°— 42 56 



