

878 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



1. Rays yellow or orange (8). 



8. Pappus of squamellae or paleae dissected into bristles above, but entire at 

 base (9). 

 9. Plant floccose- woolly , annual 88. Syntrichopappus. 



9. Plants not floccose-woolly 103. Dyssodia. 



8. Pappus otherwise (10). 



10. Leaves opposite, at least below (11). 



11. Involucre and leaves with translucent oil glands; leaf margins with a 



few stiff bristles near the base 105. Pectis. 



11. Involucre and leaves without translucent oil glands; leaves not bristly 

 at base (12). 



12. Heads large; pappus of numerous bristles 111. Arnica. 



12. Heads small; pappus of 1 or 2 bristlelike awns, or wanting. 



84. Laphamia. 

 10. Leaves alternate (13). 



13. Pappus of 2 to 8 caducous bristlelike awns; plants glutinous. 



10. Grindelia. 



13. Pappus bristles more numerous or persistent, or else the plants not 



glutinous (14). 



14. Pappus wholly of numerous simple and similar capillary bristles (15). 



15. Phyllaries proper 1-seriate, equal, sometimes with some short 



outer bractlets; style tips truncate 116. Senecio. 



15. Phyllaries in more than 1 series, usually more or less unequal and 

 graduated; style tips not truncate (16). 

 16. Heads usually small and very numerous, panicled or cymose; 

 phyllaries rarely distinctly herbaceous at apex; plants always 



herbaceous 17. Solid ago. 



16. Heads usually few and relatively large, if small and panicled, 

 then the plants shrubby; phyllaries often distinctly herbace- 

 ous at apex 18. Aplopappus. 



14. Pappus not wholly of numerous simple and similar capillary bristles 

 (17). 

 17. Shrub; heads small, few-flowered, crowded in small rounded 



terminal clusters; rays 1 or 2, small 13. Amphipappus. 



17. Herbs; inflorescence otherwise; rays more numerous, conspicuous 



(18). 



18. Achenes dissimilar, those of the rays essentially glabrous and 



epappose, the disk achenes hairy, their pappus double, the 



inner series of capillary bristles, the outer series of short 



bristles or squamellae 15. Heterotheca. 



18. Achenes all similar and with a similar (double) pappus. 



16. Chrysopsis. 



G. Hermaphrodite flowers with a tubular, regular or nearly regular corolla; rays 

 evident but sometimes small; pappus none or vestigial. 



1. Rays white, sometimes with a yellow base (2). 

 2. Receptacle naked (3). 



3. Receptacle broad and flatfish; phyllaries with a dark-brown submarginal 



line 109. Chrysanthemum. 



3. Receptacle convex, conic, or hemispheric; phyllaries not with a dark-brown 

 submarginal line (4). 

 4. Achenes oblique, ribbed only on the inner side; leaves dissected into 



linear-filiform lobes; phyllaries oblong or oval 108. Matricaria. 



4. Achenes prismatic or subterete, ribbed on all sides, or somewhat flat- 

 tened and 2-nerved; leaves entire to pinnatifid; phyllaries lanceolate 

 (5). 

 5. Achenes prismatic or subterete, ribbed on all sides. 



21. Aphanostephus. 



5. Achenes somewhat flattened, 2-nerved 23. Achaetogeron. 



2. Receptacle paleaceous (6). 



6. Rays sessile, persistent on the achenes, becoming indurated (7). 



7. Involucre strongly graduated; pales of the receptacle not cuspidate. 



52. Zinnia. 

 7. Involucre not distinctly graduated; pales of the receptacle cuspidate. 



53. Sanvitalia. 



