CARDUACEAE 



Bracts of the inflorescence lanceolate or linear-lanceolate, acute or acuminate. 



Leaves ciliate at the base. I. VIRGA-AUREAE. 



Leaves not ciliate at the base. IV. GLABERRIMAE. 



Bracts of the inflorescence oblong or linear-oblong, obtuse. 



Leaves, at least the basal ones, toothed ; stem-leaves few; plants 1-4 dm. high. 



Leaves all entire; stem very leafy, 4-8 dm. high. III. SPECIOSAE. 

 Leaves triple- veined ; heads more or less secund, on recurved-spreading branches 



(except usually in Nos. 9 and 11). 



Plants slender, not very leafy, 2-4 dm. high; stem-leaves narrowly oblanceolate 



or linear. IV. GLABERRIMAE. 

 Plant tall, leafy, 4-10 dm. high. 



Stem-leaves lanceolate. v. SEROTINAE. 



Stem-leaves obovate. VI. RADULAE. 

 Leaves densely canescent. 



^Leaves lanceolate'; bracts narrowly linear-lanceolate. V. SEROTINAE. 



Leaves, at least the lower ones, oblanceolate or obovate. VII. INCANAE. 



Bracts squarrose; leaves numerous, entire, elliptic. VIII. WARDIANAE. 



I. VIRGA-AUREAE. 



Plants low and slender, 1-3 dm. high; inflorescence corymbiform; branches with a single 



or a few corymbose heads. 

 Heads 7-9 mm. high; inner bracts linear-lanceolate, of about the same length as the 



flowers and pappus; plant 2-3 dm. high. 1. 5. scopulorum. 



Heads 5-7 mm. high; bracts lanceolate, the inner shorter than the flowers and the 



pappus; plant usually less than 2 dm. high. 2. S. ciliosa. 



Plants stout, 3-4 dm. high; inflorescence paniculate, but narrow; branches racemiform; 



heads 7-9 mm. high. 



Basal leaves broadly oblanceolate, acute; stem pubescent. 3. S. rubra. 



Basal leaves narrowly oblanceolate, obtuse; stem glabrous up to the inflorescence. 



4. S. laevicaulis. 



II. HUMILES. 



Plant low, 1-1.5 dm. high; inflorescence with few heads, short, congested. 



5. S. decumbens. 

 Plant taller, 2-4 dm. high; inflorescence with many heads, elongate. 



Leaves not ciliate; bracts oblong; inflorescence usually narrow. 6. S. oreophila. 

 Leaves ciliate at the base; bracts linear; inflorescence open. 7. S. dilatata. 



III. SPECIOSAE. 



One species. 8. S. pallida. 



IV. GLABERRIMAE. 



Heads less than 5 mm. high; stem slender. 



Inflorescence decidedly viscid; leaves indistinctly triple- veined. 9. S. viscidula. 

 Inflorescence not viscid; leaves distinctly triple- veined. 



Plant glaucous; bracts thick, oblong, obtuse. 10. S. glaucophylla. 



Plant not glaucous; bracts not thick, Iinear-lance9late to oblong-lanceolate. 

 Inflorescence narrow, scarcely secund; bracts linear-lanceolate. 



11. S. missouriensis. 

 Inflorescence usually open and more or less secund; bracts oblong-lanceolate. 



12. S. glaberrima. 

 Heads 6-7 mm. high; stem stout. 13. S. concinna. 



V. SEROTINAE. 



Inflorescence narrowly rhombic in outline; branches ascending, almost straight, scarcely 



secund. 14. S. elongata. 



Inflorescence broad; branches recurved-spreading, distinctly secund. 



Leaves green, sparingly pubescent or glabrous; pubescence scabrous, mostly confined 



to the margins and the veins. 

 Stem usually glabrous up to the inflorescence; leaves glabrous except on the margins 



and on the mid veins. 

 Veins of the leaves glabrous ; heads 5-6 mm. high, in a short panicle with strongly 



curved branches. 15. S. serotina. 



Veins of the leaves pubescent below; heads 4-5 mm. high; panicle with long 



branches. 16. S. salebrosa. 



Stem more or less pubescent. 



Heads 5 mm. or more high; leaves pubescent. 17. S. polyphylla. 



Heads about 4 mm. high; plant comparatively slender. 



Leaves pubescent, at least on the veins. 18. S. canadensis. 



Leaves glabrous, except the scabrous-ciliolate margins. 



19. S. serra. 



Leaves densely canescent, especially beneath. 

 Leaves usually broadly lanceolate. 



Leaves scabrous above. 20. S. dumetorum. 



Leaves softly puberulent on both sides. 21. S. pruinosa. 



Leaves linear-lanceolate, finely and rather softly canescent on both sides, more or 

 less yellowish gray. 22. S. ^gilvocanescens . 



