310 COMPOSITAE 



Tribe IV. INULEAE. 

 Ray-flowers wanting : disk-flowers, at least, with white or whitish corollas : 

 heads relatively small. 

 Receptacle chaffy. 19. Gifola. 



Receptacle naked. 

 Involucre of herbaceous bracts : plants more or less pubescent, not woolly. 



20. Pluchea. 

 Involucre of scarious bracts : plants woolly. 

 Plants with dioecious or polygamo-dioecious flowers. 

 Pappus-bristles of the staminate flowers thickened above : stems 



mainly creeping. 21. Antennaria. 



Pappus-bristles not thickened : stems erect. 22. Anaphalis. 

 Plants not dioecious : flowers all fruit-producing. 23. Gnaphalium. 

 Ray-flowers present and yellow : heads relatively large. 24. Inula. 



Tribe V. HELIANTHEAE. 

 Disk-flowers perfect, but not fruit-producing. 

 Achenes thick or turgid ; pappus wanting. 25. Polymnia. 



Achenes flattened : pappus present, sometimes obsolete. 

 Ray-flowers in 2 or 3 series : achenes falling away free. 



26. SiLPHIUM. 

 Ray-flowers in i series : achenes adnate to 2 or 3 bractlets and falling away 

 with them. 27. Chrysogontjm. 



Disk-flowers fruit-producing. 

 Corollas of the ray-flowers persistent on the achenes. 28. Heliopsis. 

 Corollas of the ray-flowers deciduous or wanting. 

 Pappus a cup or a crown, or of few teeth, awns or bristles. 

 Achenes, at least those of the disk-flowers, not flattened (except in Ver- 

 besina): bractlets of the receptacle mostly concave or clasping. 

 Bractlets of the receptacle subulate or bristle-like : ray-flowers with 



white ligules. 29. Eclipta. 



Bractlets of the receptacle broad. 

 Receptacle conic. 30. Rudbeckia. 



Receptacle flat or merely convex. 

 Achenes scarcely flattened, neither winged nor margined. 



31. Helianthtjs. 

 Achenes of the disk-flowers flattened, margined or winged. 



32. Verbesina. 

 Achenes very flat : bractlets of the receptacle flat or at least not clasping. 



Pappus of 2 short awns or teeth, or obsolete. 33. Coreopsis. 

 Pappus of 2-6 awns or teeth, upwardly or downwardly barbed. 



34. Bidens. 

 Pappus of numerous scales. 



Heads with ray-flowers ; leaves opposite ; blades toothed. 



35. Galinsoga. 

 Heads without ray-flowers ; .leaves alternate ; blades entire. 



36. Marshallia. 



Tribe VI. HELENIEAE. 

 A single genus in our range. 37. Helenium. 



Tribe VII. ANTHEMIDEAE. 

 a. Receptacle chaffy. 

 Involucre obovoid to campanulate ; heads small : achenes flattened, 



38. Achillea. 



