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

18. Brachychæta. Heads 8–10-flowered, clustered; rays 4 or 5. Pappus a row of minute bristles shorter than the achene.

[*] 2. Ray-flowers white, blue, or purple, never yellow.

[+] Pappus none or very short, with or without a few awns.

[++] Receptacle conical. Awns none.

19. Bellis. Achenes marginless, flattened; pappus none. Involucral scales equal.

20. Aphanostephus. Achenes prismatic; pappus coroniform. Outer scales shorter.

[++][++] Receptacle flat or convex. Pappus usually with awns.

21. Chætopappa. Achenes fusiform; pappus of 5 or fewer thin chaff and alternating awns. Western.

22. Boltonia. Achenes very flat, thick-winged; pappus of short bristles and usually 2–4 awns.

[+][+] Pappus of a single row of awns or coarse rigid bristles, or in the ray scale-like.