126 PLANTS OF YELLOWSTONE NATIONAL PARK 
head. The narrow, rigid leaves are entire and one-nerved, and 
usually less than half an inch long. The ray flowers are light violet. 
Tleabane (Erigeron) .—The fleabanes can usually be distinguished 
from the asters by the fact that the bracts of the involucre are in only 
1 or 2 rows instead of several. Usually the ray flowers are 
narrower and more numerous. Nineteen species have been identified 
in the park, and these may be distinguished by means of the follow- 
ing key: 
1. Rays inconspicuous and very short. 2. 
1. Rays conspicuous, longer than the width of the disk. 4. 
2. Plants usually more than a foot high. Stem usually purplish and solitary. 
Erigeron lapiluteus. 
2. Plants usually less than a foot high. 
Stems usually several, green. 3. 
3. Leaves narrow, at least some of them 
linear. Erigeron lonchophyllus. 
3. Leaves broader, none of them linear. 
Erigeron acris. 
4. Plants usually more than a foot 
high. 5. 
4. Plants usually less than a foot high. 9. 
5. Ray flowers rather broad, giving the 
appearance of an aster. Alaska 
fleabane ( Erigeron salsuginosus ). 
5. Ray flowers narrow and numerous. 6. 
6. Upper stem leaves greatly reduced in 
size. Erigeron as per. 
6. Upper stem leaves not much reduced 
in size. 7. 
7. Leaves few and far apart. Erigeron 
superbus. 
7. Leaves more numerous. 8. 
8. Bracts of the involucre smooth. Erig¬ 
eron macranthus. 
8. Bracts of the involucre hairy. Oregon 
fleabane ( Erigeron speeiosus). 
10. Leaves 2 or 3 times ternate. Erigeron compos itus. 
10. Leaves simple. 11. 
11. Leaves all entire, mostly linear. Erigeron pumilis. 
11. Leaves somewhat broader, the lower ones toothed. Erigeron ramosus. 
12. Stems mostly unbranched and bearing a single head. 13. 
12. Stems branched and bearing several heads. 15. 
13. Involucre woolly. Erigeron uniflorus. 
13. Involucre not woolly. 14. 
14. Stems usually less than 4 inches high. Leaves all narrow, mostly linear. 
Erigeron radicatus. 
14. Stems usually more than 4 inches high. Leaves somewhat broader. 
Erigeron ursinus. 
Figure 102.—Oregon fleabane. Blue or 
violet. Photograph by A. R. Sweetser. 
9. Rays yellow. Erigeron luteus. 
9. Rays white. 10. 
9. Rays violet or purple. 12. 
