COMPOSITAE. 315 



Involucre of 4 bracts; twining, herbaceous vines. 



5. Willughbaeya. 

 Achenes 8-10-ribbed, or 8-10-striate. 



Bracts of the involucre strongly Rtriate-nerved ; heads panicled or 



corymbed. 6. Kuhnia. 



Bracts of the involucre faintly striate, if at all; heads spiked or 

 racemed. 7. Lacinaria. 



Tribe 3. ASTEEEAE. 



A. Bay-flowers yellow (white in one species of Solidago) or wanting; plants 



not dioecious. 

 Pappus of scales, or awns, or wanting, never of numerous capillary 



bristles. , 8. . Grindelia. 



Pappus of either the radiate or tubular flowers, or both, of numerous 

 capillary bristles, with or without an outer series of shorter ones, 

 or of scales. 

 Pappus, at least of the disk-flowers, double, an inner series of capil- 

 lary bristles, and an outer one of scales or short bristles; 

 heads large. 

 Achenes of the ray-flowers thick, the pappus obsolete, or of a 

 few caducous bristles; achenes of the disk-flowers flat. 



i 9. Heterotheca. 



Achenes of both ray-flowers and disk-flowers flattened. 



10. Chrysopsis. 

 Pappus wholly of capillary bristles. 



Receptacle alveolate; rays mostly not more numerous than the 



disk-flowers. 11. Solidago. 



Beceptacle' fimbrillate; rays more numerous than the disk- 

 flowers;, heads corymbose-paniculate. 12. Euthamia. 



B. Bay-flowers present, not yellow. 



Pappus a mere crown, or of a few awns or bristles, or wanting, never of 

 numerous capillary bristles. 

 Beceptacle conic. 13. Bellis. 



Beceptacle flat, or somewhat convex. 14. Boltonia. 



Pappus of numerous capillary bristles. 



Pappus a single series of capillary bristles ; sometimes with an outer 

 series of shorter ones. 

 Bracts of the involucre in 2 to many series. 



Involucre narrow, its bracts firm; rays few, white. 



15. Sericocarpus. 

 Involucre turbinate to hemispheric, bracts mostly thin; 



rays usually numerous, white to purple. 



16. Aster. 



Bracts of the involucre in only 1 or 2 series, very narrow; 

 heads mostly long-peduncled. 

 Bays longer than the diameter of the disk. 



17. Erigeron. 

 Bays not longer than the diameter of the disk; heads very 



small, panicled. 18. Leptilon. 



Pappus distinctly double, the inner bristles long, the outer shorter. 

 Leaves lanceolate, ovate, or obovate; rays white. 



19. Doellingeria. 

 Leaves narrowly linear; rays violet. 20. Ionactis. 



C. Bay -flowers none ; dioscious shrubs ; ; pappus capillary. 



21. Baccharis. 

 Tribe 4. INTJLAE. 



Heads small, rays none; flowers white or whitish. 



Beceptacle chaffy. 22. Gifola. 



Beceptacle naked. 



Bracts of the involucre not searious; plants pubescent or glabrous, 

 not woolly. 23. Pluchea. 



