The Manual of the Botany of the Northern United States / Including the District East of the Mississippi and North of North Carolina and Tennessee

by Asa Gray

[+][+] Involucre of one or more rows of separate scales.

[++] Chaff of the flat receptacle bristle-shaped.

46. Eclipta. Ray short. Involucral scales 10–12, in two rows, herbaceous.

[++][++] Chaff scale-like, embracing or subtending the achenes.

[=] Receptacle high, conical or columnar in fruit. Pappus none or a short crown.

47. Heliopsis. Rays fertile. Achenes 4-sided. Leaves opposite.

48. Echinacea. Rays rose-colored, pistillate, sterile. Achenes short, 4-sided. Chaff spinescent.

49. Rudbeckia. Rays neutral. Achenes 4-sided, flat at the top, marginless.

50. Lepachys. Rays few, neutral. Achenes flattened laterally and margined.

[=][=] Receptacle flat to convex. Achenes not winged nor very flat.