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CAKDUACEAE. 



Tribe I. VERNONIEAE. 

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



1. Vernonia. 



Tribe II. EUPATOBIEAE. 



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. MiTcania. 



Tribe III. ASTEREAE. 



Ray-florets present ; plants not dioecious. 

 Ray-florets ligular. 



Ligules yellow ; pappus copious, ray-achenes flattened. 5. Chrysopsis. 

 Ligules white or colored (not yellow). 

 Involucral bracts in 3-5 series. 



Ligules long and narrow ; bracts mainly herba- 

 ceous. 6. Aster. 

 Ligules short and broad ; bracts not herbaceous. 7. Gundlachia. 

 Involucral bracts in 1-2 series. 



Ligules longer than the diameter of the disk. 8. Erigeron. 

 Ligules shorter than the diameter of the disk. 9. Leptilon. 

 Ray-florets tubular ; pappus 2-serial. 10. EschenbacTiia. 



Ray-florets wanting ; plants dioecious. 11. Baccharis. 



Tribe IV. INULEAE. 



Bracts broad ; plants leafy throughout. 

 Bracts narrow ; plants leafy only at the base. 



12. Pluchea. 



13. Sachsia. 



Tribe V. HELIANTHEAE. 



Disk-florets perfect but not fruit-producing. 

 Achenes not flattened. 



Fruit unarmed ; achenes quadrangular. 14. Tetranthus. 



Fruit armed with hooked prickles. 15. Acanthospermum. 



Achenes markedly flattened. 16. Parthenium. 



Disk-florets fruit-producing. 



Ray-florets persistent on the achenes. 17. Crassina. 



Ray-florets not persistent on the achenes or wanting. 



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



bristles. 

 Achenes not compressed. 



Chaff of the receptacle mere awns or bristles. 18. "Fer&esina. 



Chaff of the receptacle concave or clasping. 



Pappus of slender caducous awns. 19. Melanthera. 



Pappus wanting. 



Achenes sharp-edged, 4-6-angled. 20. Isocarpha. 



Achenes of the disk neither sharp-edged, 



margined nor winged. 



Achenes acutely 4-angled. 21. Borrichia. 



Achenes indistinctly 4-angled. 22. Wedelia. 



Achenes of the disk broadly white-winged. 23. Ximenesia. 

 Achenes markedly flattened parallel with the invo- 



lucral bracts. 



Involucre single. 24. Synedrella. 



Involucre double. 



Pappus of 2 short cornuate awns. 25. Salmca. 



Pappus of 2-4 long barbed awns. 26. fiidens. 



Pappus of numerous plumose ci'liate scales. 27. Tridax. 



Tribe VI. HELENIEAE. 

 glands ; bracts of the involucre 



Plant-tissues without oil 



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. Neothymopsis. 



30. Porophyllum. 



31. Pectis. 



Tribe VII. SEOVECIONEAE. 



Bracts of the involucre markedly overlapping. 32. Neurolaena. 

 Bracts of the involucre slightly if at all overlapping. 



Achenes elongated, sharply 5-ribbed. 33. Emilia. 



Achenes short, pilose-striate. 34. Erechthites. 



