14(13). Rhizomatous or stoloniferous perennials 11. Aster, p. 1615 



14. Taprooted annuals (15) 



15(14). Leaves deeply serrate or pinnatifid 9. Machaeranthera, p. 1609 



15. Leaves or most of them entire 11. Aster, p. 1615 



16(2). Pappus solely of short or elongate scales, with no bristlelike members 

 either in ray or disk 7. Xanthocephalum, p. 1608 



16. Pappus with at least some bristlelike members (17) 



17(16). Leaf blades bristly-serrate, pinnatifid or pinnately parted 



9. Machaeranthera, p. 1609 



1 7. Leaf blades entire or merely toothed (18) 



18(17). Stems strictly erect, topped by flat or roughly corymbiform aggregations 



of stems and heads; heads 4-6 mm. high including the flowers 



8. Euthamia, p. 1609 



18. Plants not corymbiform or if somewhat corymbiform the heads larger 



10. Solidago, p. 1610 



IV. Key to Genera of Inuleae 



1. Phyllaries mostly scarious 17. Gnaphalium, p. 1631 



1. Phyllaries not mostly scarious (2) 



2(1). Pappus members of the staminate (central) flowers of the head flattened, 

 whitish, bristlelike, near the tip discolored brownish and about 

 twice as broad as in the lower part 19. Tessaria, p. 1637 



2. Pappus members not broadened upward 18. Pluchea, p. 1633 



V. Key to Genera of Heliantheae 



1 . Ray flowers fertile but with corollas reduced to a vestige or a minute tube with 

 oblique orifice, or fertile heads burlike and lacking staminate 

 flowers (2) 



1. Ray flowers when present with better developed corollas or else infertile (5) 



2(1). Heads with both fertile ray flowers and staminate disk flowers, never 

 burlike (3) 



2. Heads unisexual (4) 



3(2). Receptacle chaffy throughout; involucral bracts in one or more series, 

 usually not enclosing the achenes 20. Iva, p. 1637 



3. Receptacle chaffy only near the margin; involucral bracts uniseriate, equal, 



strongly carinate, each enfolding a ray achene; heavy-scented 

 annuals 21. Madia, p. 1642 



4(2). Phyllaries of staminate heads free from each other; pistillate heads burlike 

 23. Xanthium, p. 1646 



4. Phyllaries of staminate heads coalescent partially 22. Ambrosia, p. 1642 



5(1). Ray flowers absent; disk corolla white, cream or pale-lavender or pale- 

 purplish, deeply parted into 5 long linear obtuse lobes 



36. Marshallia, p. 1675 



5. Plants not having the same combination of characters (6) 



6(5). Achenes markedly dorsiventrally flattened (7) 



6. Achenes (at least those of the disk) flattened laterally or not flattened at 



all (10) 



7(6). Involucre uniseriate, green; depressed or sprawling yellow-headed perennial 

 herbs 32. Calyptocarpus, p. 1660 



7. Involucre at least seemingly double; usually erect herbs (8) 



1590 



