360 CARDUACEAE. 



I. ACRES. 



Bracts of the involucre linear, abruptly acute, never glandular ; inflorescence 



racemiform with almost erect branches. 

 Low, 1-2 dm. high; stem-leaves sessile; peduncles short. 



i. E. minor. 

 Taller, 3-6 dm. high, lower stem-leaves petioled ; basal leaves oblanceolate ; 



peduncles elongated. 2. E. lonchophyllus. 



Bracts of the inflorescence linear-subulate, long-attenuate, and more or less 

 glandular-puberulent ; inflorescence inclined to be corymbiform or paniculate ; 

 branches ascending. 



Bracts glandular-puberulent, rarely with a few hairs. 3. E. droebachiensis. 

 Bracts hirsute or both hirsute and glandular-puberulent. 



Plant tall, 3-6 dm. high, apparently only biennial ; heads numerous. 



4. E. yellowstonensis. 

 Plant low, 1-3 dm. high, perennial ; heads few. 5. E. jucundus. 



II. MULTIFIDI. 



Leaves pinnately divided. 6. E. pinnatisectus. 



Leaves once to thrice ternately divided. 

 Leaves twice or thrice ternate. 



Ultimate divisions of the leaves narrowly linear ; peduncles with long linear 



leaves. 7. E. compositus. 



Ultimate divisions of the leaves spatulate or broadly oblanceolate ; peduncles 



naked above or with very short leaves. 8. E. multifidus. 



Leaves once ternate or quinate. 9. E. trifidus. 



III. UNIFLORI. 



Involucres and peduncles with black-purple hairs. 10. E. melanocephalus. 

 Involucres and peduncles white-hairy. 



Plant 5-8 cm. high; disk 10-12 mm. wide. n. E. uniftorus. 



Plant i dm. high or more; disk 13-15 mm. wide. 12. E. leucotrichus. 



IV. RADICATI. 

 Involucre glandular-puberulent or glabrate, not hirsute. 



Stem and leaves glabrous or nearly so. 13. E. l$iomeris. 



Stem and leaves pubescent and somewhat glandular. 36. E. viscidus. 

 Involucre more or less hirsute or strigose ; in some also slightly glandular- 

 puberulent. 

 Leaves and stem glandular-scabrous as well as hirsute. 



14. E. glandulosus. 

 Leaves and stem hirsute or strigose, not glandular. 



Stem i dm. or more high, appressed-pubescent ; disk over i cm. wide : 



branches of the caudex rather slender, purplish. 

 Leaves narrowly linear-oblanceolate, 1-3 mm. wide, strigose. 



23. E. Engeltnannii. 

 Leaves oblanceolate to linear-oblanceolate, 3-8 mm. wide, glabrous above 



except the margins. 15. E. ursinus. 



Stem 4-7 cm. high ; disk less than i cm. wide ; caudex and its branches stout 



and short, not purplish. 

 Leaves linear-oblanceolate to spatulate. 



Stem with appressed hairs. 16. E. Peasei. 



Stem with more or less spreading hairs. 17. E. vetensis. 



Leaves linear-filiform. 18. E. nematophyllus. 



V. PUMILI. 

 Rays present. 



Ray-flowers white ; the outer pappus of small inconspicuous bristles. 



19. E. pumilus. 

 Ray-flowers blue or purplish ; outer pappus conspicuous and squamellate. 



20. E. concinnus. 

 Rays wanting. 21. E. aphanactis. 



