8(7). Pappus of 2 barbless teeth, a mere crown or absent 



33. Coreopsis, p. 1660 



8. Pappus mostly of retrorsely or antrorsely barbed or hispid awns or teeth 



(essentially absent in Bidens aristosa and B. polylepis) (9) 



9(8). Achenes beaked 35. Cosmos, p. 1672 



9. Achenes not beaked 34. Bidens, p. 1663 



10(6). Chaff of the receptacle merely awns or bristles, or pappus awn solitary 



(11) 



10. Chaff of concavo-convex or folded pales; pappus usually more than 1 awn 



(12) 



11(10). Rays very numerous, usually less than 3 mm. long; disk achenes 



markedly corky-margined; ray achenes often abortive 



24. Eclipta, p. 1646 



11. Rays 5 to 10, 7-12 mm. long; disk achenes not corky-margined 



25. Tithonia, p. 1649 



12(10). Receptacle conic, subulate or columnar (13) 



12. Receptacle flat or convex (16) 



13(12). Ray flowers fertile and styliferous; style branches truncate or penicillate; 

 leaves opposite 26. Spilanthes, p. 1649 



13. Ray flowers infertile and styleless; style branches of disk flowers with acute 



or obtuse appendages; leaves mostly alternate (14) 



14(13). Receptacle conical 27. Rudbeckia p. 1651 



14. Receptacle columnar, cylindric or conic-cylindric at maturity (15) 



15(14). Receptacle cylindric or conic-cylindric; phyllaries 2- or 3-seriate, sub- 

 equal 27. Rudbeckia, p. 1651 



15. Receptacle columnar; phyllaries 2-seriate, the inner ones half or less than 



half as long as the outer 28. Dracopis, p. 1652 



16(12). Disk achenes thin-edged, knife-edged or winged 



31, Verbesina, p. 1659 



16. Disk achenes often somewhat flattened but the two thin edges not sharp nor 



winged (17) 



17(16). Ray flowers fertile; maritime rhizomatous subshrubs of saline habitats 

 29. Borrichia, p. 1655 



17. Ray flowers sterile 30. Helianthus, p. 1655 



VI . Key to Genera of Helenieae 



1. Phyllaries in 3 to 5 series, imbricated, the outer ones shorter than the inner; 

 receptacle bristly around the sockets 38. Clappia, p. 1681 



1. Phyllaries in 1 or 2 series, nearly equal in length, rarely with 1 to 3 small 



outer calyculate ones (2) 



2(1). Achenes columnar, lO-ribbed, rarely slightly flattened....39. Flaveria, p. 1683 



2. Achenes distinctly 3- to 5-angled or if less distinctly so then obconic 



37. Helenium, p. 1677 



VII. Key to Genera of Anthemideae 



1. Receptacle chaffy at least near the center (2) 



1. Receptacle naked or hairy around the sockets (3) 



2(1). Receptacle high-conic; disk corolla greenish-yellow; heads solitary 



40. Anthemis, p. 1686 



2. Receptacle not high-conic; disk corolla whitish; heads in corymbiform aggre- 



gations 41. Achillea, p. 1686 



1591 



