Compositaceae A15 
GROUP | 
A. Stems always almost equally leafy to the top, mostly clustered. 
B. Heads 16—25 mm. high. E. 
S. megacephalus Nutt. 
BB. Heads 8—12 mm. high. 
C. Stems 1—3 dm. high. 
D. Leaves orbicular to obovate, 2.5—4 cm. long. E. 
S. streptanthifolius Gr. 
DD. Most of the leaves narrower than obovate, |—2.5 cm. long. 
E. Leaves entire to crenately few-toothed. U. 
S. hesperius Gr. 
EE. Leaves or some of them sharply toothed to pinnatifid-dentate. W. C. 
E. (S. occidentalis; S. ductoris.) 
S. fremontii T. & G. 
CC. Stems 4—10 dm. high. 
F. Leaves sessile; the blade lanceolate. 
G. Leaf-margin evenly serrate. E. 
S. serra Hook. 
GG. __Leaf-margin entire. C. E. (S. serra integriusculus. ) 
S. serra lanceolatus Pip. 
FF. Leaves petioled; the blade triangular-lanceolate, coarsely dentate. 
H. Herbage nearly glabrous. W.C. E. (S. gibbonsii.) 
S. triangularis Hook. 
HH. Herbage densely floccose-woolly. W.C. E. (S. subvestitus.) 
S. triangularis subvestitus Greenm. 
AA. Stems either few-leaved or the upper leaves reduced in size, usually solitary. 
I. Herbage wholly glabrous. 
J. Leaves glaucous, mostly entire. C. E. (S. hydrophyllus of How. FI.) 
S. hydrophilus Nutt. 
JJ. Leaves not glaucous, mostly dentate. 
K.  Involucre-bracts 6—7 mm. long, straw-colored. C. E. 
S. hydrophiloides Rydb. 
KK.  Involucre-bracts 7—8 mm. long, brownish. C. E. 
S. foetidus How. 
II. Herbage somewhat hairy. 
L. Heads rayless. C. E. 
S. vaseyi Greenm. 

LL. Heads radiate. 
M. Herbage permanently white-tomentose. 
N. Plant 1—-3 dm. high; lowest leaves entire. E. (S. altus.) 
S. Iugens Rich. 
NN. Plant 6—I10 dm. high; lowest leaves somewhat dentate. E. (S. 
howellii; S. canus purshianus; S.  purshianus.) 
S. canus Hook. (Silvery Rag-wort) 
MM. Herbage often tomentose when young but becoming glabrate. 
O. Heads in a dense cluster, 3—6. E. 
S. condensatus Gr. 
OO. Heads in a loose cluster, usually more than 6. 
P. Involucre-bracts about 13. W. C. E. (S. exaltatus ochraceus; S. 
cordatus; S. glaucescens.) S. exaltatus Nutt. 
PP. Involucre-bracts about 21. E.  (S. columbianus.) 
S. atriapiculatus Rydb. 

