120 
PLANTS OF YELLOWSTONE NATIONAL PARK 
19. Heads more than 2 inches broad. Balsamroot (Balsamorrhiza sagittata) 
(p. 129) 
19. Heads less than an inch broad. 20. 
20. Rays purple. Oreastrum haydeni __(p. 125) 
20. Rays yellow. 21. 
21. Rays 8 to 12. Stenotus caespitosus _(p. 122) 
21. Rays 30 to 40. Erigeron luteus ----(p. 126) 
22. Leaves all opposite. Arnica ( Arnica) _._(p. 133) 
22. Lower leaves opposite, some of the upper ones alternate. 23. 
22. Leaves mostly alternate. 24. 
23. Fruits flat, very strongly compressed. Awns 2, persistent. Helianthella 
(p. 131) 
23. Fruits rather plump, more or less rounded on the sides. Awns usually 2, 
deciduous. Sunflower ( Helianthus) __(p. 130) 
24. Ray flowers not yellow. 25. 
24. Ray flowers yellow. 31. 
25. Pappus none. 26. 
25. Pappus crownlike with several teeth. Heads large. Rays white. White 
mule-ears (Wyethia helianthoides )_____(p. 130) 
25. Pappus of bristles. 27. 
26. Heads small, numerous, white; plants very aromatic. Yarrow (Achillea 
lanulosa). ______________ ---____(p. 132) 
26. Heads large, rays white. Oxeye daisy (Chrysanthemum leucanthemum) 
(p. 132) 
27. Bracts of the involucre in only 1 or 2 rows. Fleabane ( Erigeron )_(p. 126) 
27. Bracts of the involucre in more than 2 rows. 28. 
28. Heads about 2 inches broad. Townsendia parryi _____w (p. 122) 
28. Heads smaller. 29. 
29. Rays few (8 to 16). Involucre somewhat resinous. Machaer anther a 
pulverulenta __________(p. 124) 
29. Rays usually more than 16. Involucre not resinous. 30. 
30. Plants dwarf. Each stem bearing a single head. lonactis oZpma___(p. 125) 
30. Plants not dwarf. Stems usually branching and bearing several heads. 
Aster (Aster) ___ __(p. 123) 
31. Shrubs. Macronema grindelioides _(p. 139) 
31. Herbs. 32. 
32. Involucre very gummy or sticky. 33. 
32. Involucre not gummy or sticky. 34. 
33. Ray flowers only 5 or fewer. Tarweed (Madia glomerata) _(p. 131) 
33. Ray flowers more than 5. Gumplant (Grindelia subalpina )_(p. 121) 
34. Pappus of scales or awns. 35. 
34. Pappus, in part at least, of hairlike bristles. 38. 
35. Disk flowers brownish. 36. 
35. Disk flowers yellow. 37. 
36. Plant 3 to 6 feet high. Disk 1 to 2 inches broad. Common sunflower (Hel¬ 
ianthus annuus) _(p. 130) 
36. Plant 1 to 3 feet tall. Disk about half an inch broad. Prairie sunflower 
(Helianthus scaberrimus) _(p. 130) 
37. Plants more or less woolly. Eriophyllum integrifolium ___(p. 131) 
37. Plants hairy but not woolly. Gaillardia (Gaillardia aristata) _(p. 131) 
37. Plants neither hairy nor woolly. Broom snakeweed (Gutierrezia sarothrae) 
(p. 121) 
38. Pappus yellowish brown or yellowish gray. Pyrrocoma _(p. 122) 
38. Pappus white or whitish. 39. 
