186 



CABDUACEAE. 



A. Flowers all tubular, the heads discoid. (See Emilia, Senecio vulgaris and Bidens 



pilosa.) 

 Anthers not tailed at the base. 



Flowers perfect. 1. Eupatorium. 



Flowers dioecious. 2. Baccharis. 



Anthers tailed at the base. 



Bracts of the involucre not scarious, 3. Pluchea. 



Bracts of the involucre scarious. 4. Gnaphalium. 



B. Flowers both tubular and radiate (except Emilia, Senecio 



vulgaris and sometimes Bidens pilosa). 

 1. Receptacle naked. (See Chrysanthemum.) 



Bracts of the involucre imbricated in 2-several series. 

 Rays yellow. 

 Rays white. 



Bracts imbricated in several series. 

 Bracts imbricated in few series. 



Rays longer than the diameter of the disk ; 



heads few. 

 Rays shorter than the diameter of the disk ; 

 heads many, panicled. 

 Bracts of the involucre in one series, sometimes with 

 a few. short outer ones. 

 Style-branches unappendaged. 

 Style-branches appendaged. 



2. Receptacle chaffy or scaly (except in Chrysanthemum). 

 Bracts of the involucre not scarious. 

 Disk-flowers perfect, but sterile. 

 Achenes thick, not flattened. 

 Achenes flattened. 

 Disk-flowers fertile. 



Pappus cup-like or of a few teeth or bristles. 

 Achenes not flattened. 



Scales of the receptacle awn-like. 

 Scales of the receptacle broad. 



Low, fleshy, coastal or salt marsh shrubs. 

 Tall herbs, not fleshy. 

 Achenes very flat, 2-6-awned. 

 Pappus of numerous scales. 

 Bracts of the involucre scarious. 

 Receptacle chaffy. 



Achenes flattened : heads small. 

 Achenes terete ; heads large. 

 Receptacle naked. 



5. Solidago. 



6. Aster. 



7. Erigeron. 



8. Leptilon. 



9. Senecio. 

 10. Emilia. 



11. Polym^nia. 



12. Parthenium. 



13. Verhesina. 



14. Borrichia. 



15. Helianthus. 



16. Bidens. 



17. Galinsoga. 



18. Achillea. 



19. Anthemis. 



20. Chrysanthemum. 



1. EUPATORIUM [Tourn.] L. 



Erect perennial herbs, with, opposite or verticiliate, or sometimes alternate^ 

 often punctate leaves, and in our species cymose-paniculate discoid heads of 

 perfect white or greenish flowers. Involucre oblong, ovoid, campanulate, or hemi- 

 spheric, the bracts imbricated in 2-several series. Eeceptacle naked. Corolla 

 regular, its tube slender, its limb 5-lobed or 5-toothed. Anthers obtuse and 

 entire at the base, appendiculate at the apex. 'Style-branches elongated, flat- 

 tened, or thickened above, stigmatic at the base. Achenes 5-angled, truncate. 

 Pappus of numerous capillary usually scabrous bristles arranged in 1 row. 

 [Named for Mithridates Eupator, i. e., of a noble father.] Over 500 species, 

 mostly of warm or tropical regions. Type species: Eupatorium cannabinum L. 



Leaves dissected into filiform segments. 

 Leaves oblong to ovate, dentate or serrate. 



Leaves broadly triangular-ovate. 



Leaves oblong to oblong-lanceolate. 



1. E. capilli folium. 



2. E. adenophorum. 



3. E. riparium. 



