236 American Midland Naturalist Monograph No. 7 



41.Achenes flattened. 



44. Rays numerous ; bracts thick, in several rows ; coarse 

 herbs with resinous sap ; disk-flowers perfect but 



sterile 26. Silphium 



44. Rays mostly 8; bracts in two series; disk-flowers 



fertile 37. Coreopsis 



40. Leaves alternate or basal. 



45. Leaves or some of them deeply lobed or divided; stem 

 not winged. 

 46. Receptacle conical to columnar. 



47. .\chenes flattened, sharp-margined or winged 



32. Ratibida 



47. Achenes 4-sided, not at all margined or winged 



30. Rudbeckia 



46. Receptacle flat or convex; achenes flattened, 2- 



winged, notched at the apex 26. Silphium 



45. Leaves serrate or entire. 



48. Stems scapose; leaves all basal. 



49. Leaves large, ovate, toothed, long-petioled; scapes 



2-3 m tail; heads several 26. Silphium 



49. Leaves small, spatulate, entire; scapes 5-15 cm 



tall; heads solitary 40. Actinea 



48. Stems leafy. 



50. Stems more or less winged by the decurrent bases 



of the leaves (except Helenium tenuifolium) . 

 51. Rays 3-lobed, 10-18; pappus of 5-8 acuminate 



or aristate scales 41. Helenium 



51. Rays entire or emarginate; pappus of 2 subu- 



late awns 35. Verbesina 



50. Stems not winged. 



52. Receptacle conical; pappus a mere crown, or 



none; disk-flowers purple 30. Rudbeckia 



52. Receptacle flat or convex; pappus of 2 decidu- 

 ous, translucent scales or awns ; disk-flowers 



yellow or brownish 34. Helianthus 



35. Rays not yellow. 



53. Leaves opposite; ray-flowers small, white. 



54. Leaves angulate-lobed, thin, dilated at the base; plants 

 glandular-pubescent; corolla- tube of the ray-flowers 

 pubescent 25. Polytnnia 



54. Leaves serrate. 



55. Leaves ovate, petioled 33. Galinsoga 



55. Leaves lanceolate, sessile 29. Eclipta 



53. Leaves alternate or basal. 



56. Leaves all basal, obovate; heads solitary; bracts about equal, 



obtuse, usually purplish; pappus a mere crown 17. Bellis 



56. Leaves cauline and basal. 



57. Leaves dissected or incised; bracts scarious. 



58. Rays 4-6, short; heads numerous 43. Achillea 



58. Rays 10-30; heads fewer. 



59. Leaves cut into filiform divisions; receptacle 



chaffy 44. Anthemis 



