434 



CARDUACEAE. 



Tribe I. Veenonieae. 

 Pappus of 2 series ; bracts of involucre usually not appendaged. 1. Vernonta. 



Tribe II. Eupatohieae. 



Pappus of scales. 2. Ageratum. 

 Pappus of capillary bristles. 



Involucre of more than 4 bracts. 5-many-flowered. 3. Eupatorium. 



Involucre of 4 (rarely more) bracts, 4-flowered. 4. Mikania. 



Tribe III. Asteheae. 



Bay-florets present ; plants not dioecious. 

 Ray-florets ligular. 



Ligules yellow ; pappus copious, ray-achenes flattened. 

 Ligules white or colored (not yellow). 

 Involucral bracts in 3-5 series. 



Ligules long and narrow ; bracts mainly herba- 

 ceous. 

 Ligules short and broad ; bracts not herbaceous. 

 Involucral bracts in 1-2 series. 



Ligules longer than the diameter of the disk. 

 Ligules shorter than the diameter of the disk. 

 Ray-florets tubular ; pappus 2-serial. 

 Ray-florets wanting; plants dioecious. 



5. Chrysopala. 



6. Aster. 



7. Oundlachta. 



8. Brigeron. 



9. Leptilon. 



10. Eschenbachia. 



11. Baccharis. 



Tribe IV. Ikuleae. 



Bracts broad ; plants leafy throughout. 

 Bracts narrow ; plants leafy only at the base. 



12. PUichea. 



13. Sachsia. 



Tribe V. Heliaktheae. 



Disk-florets perfect but not fruit-producing. 

 Aehenes not flattened. 



Fruit unarmed ; aehenes quadrangular. 14. 



Pruit armed with hooked prickles. 15. 



Aehenes markedly flattened. 16. 



Disk-florets fruit-producing. 



Bay-florets persistent on the aehenes. 



Ray-florets not persistent on the aehenes or wanting. 



Pappus a mere crown or cap, or of few teeth, awns or 

 bristles. 

 Aehenes not compressed. 



Chaff of the receptacle mere awns or bristles. 18. 



ChalE of the receptacle concave or clasping. 



Pappus of slender caducous awns. 19. 



Pappus wanting. 



Aehenes sharp-edged, 4— 6-an'gled. 20. 



Aehenes of the disk neither sharp-edged, 

 margined nor winged. 

 Aehenes acutely 4-angleil. 21. 



Aehenes indistinctly 4-angled. 22. 



Aehenes of the disk broadly white-winged. 23. 

 Aehenes markedly flattened parallel with the invo- 

 lucral bracts. 

 Involucre single. 

 Involucre double. 



Pappus of 2 short comuate awns. 25. 



Pappus of 2-4 long barbed awns. 26. 



Pappus of numerous plumose ciliate scales. 27. 



Tetranthus. 



Acanthospermum. 



Parthenium. 



17. Crassina. 



Yerbesina. 



Melanthera. 



Isocarpha. 



Borrichia. 



Wedelia. 



Ximenesia. 



24. Synedrella. 



Salmea. 

 Bidens. 

 Tridax. 



Tribe VI. Helenieae. 



Plant-tissues without oil glands; bracts of the involucre 



united below. 

 Plant-tissues with oil glands; bracts separate. 

 Involucral bracts 2-seriate ; pappus a crown. 

 Involucral bracts 1-seriate. 



Pappus of copious capillary bristles. 

 Pappus of a few sharp awns. 



28. Flaveria. 



29. Neothymopsla. 



30. Porophyllum. 



31. Pectia. 



Tribe VII. Senecioneab. 



Bracts of the involucre markedly overlapping. 

 Bracts of the involucre slightly If at iill overlapping. 



Aehenes elongated, sharply 5-ribbed. 



Aehenes short, pilose-striate. 



32. Neurolaena. 



33. Emilia. 



34. Erechthitea. 



