THISTLE FAMILY 1005 



Bracts narrow, with weak or slender spines. 



Braces greenish, sometimes slightly arachnoid on the margins, but not 



floccose; lobes of the leaves obtuse. 25. C. oreophilum. 



Bracts slightly floccose when yoimg; lobes of the leaves acute. 



Involucral spines more or less spreading; bracts yellowish; leaves 



slightly lobed. 15. C. nevadense, 



Involucral spines ascending; bracts greenish; leaves deeply lobed. 



26. C. olivescens. 

 Inner bracts with conspicuous dilated, ovate or lanceolate, erose and twisted tips. 



Leaves not at all tomentose; heads usually soUtary; corollas rose-purple. 



27. C. Druimnondii, 

 Leaves more or less tomentose beneath; heads usually clustered; corollas white or 



pale rose. 

 Heads on short branches soUtary in the axils of the leaves. 



28. C magnijicum. 



Heads subsessile and clustered at the end of the stem. ^ 



Plant more or less arachnoid as well as tomentose; leaves Imear m outlme. 



29. C foliosum. 



Plant not arachnoid, dark green; leaves broader. 30. C. lacerum. 



VIII. PULCHELL.V. 



Leaves glabrous or at least glabrate in age. , ^ ^ 



Spines of the middle bracts fully 1 cm. long and longer than the bracts 



31. C. diffusum. 



Spines of the middle bracts 3-7 mm. long, shorter than the bracts. 

 Divisions of the leaves linear to triangular; involucre campanulate. 



Divisions of the leaves linear or linear-lanceolate, often agam pmnatmd; 



leaves scarcelv decurrent. 32. C bipmnatum. 



Divisions of the leaves ovate or triangular; leaves conspicuously decurrent. 



33. C. calcareum. 



Divisions of the leaves semi-orbicular, rounded-ovate; involucre hemispheric. 



34. C lactucinum. 



Leaves permanently tomentose, at least beneath. ^ ,. t-.i 



Tips of the inner bracts chartaceous, yellow, spreading, and shghtly erose. 



35. C. spathulatum. 



Tips of the inner bracts soft, erect and usually purplish. - ^ ^ .^ , 



Spines of the middle bracts more than 1 cm. long, stout. 36. C. nidulum. 

 Spines of the middle bracts 3-6 mm. long, slender. , . , 



Divisions of the leaves narrow; corolla rose-purple; mvolucre narrow. 



37. C. pulchellum. 



Divisions of the leaves broad and short, ovate; corollas crimson; involucre 

 broad, ^^- ^- cirizonicum, 



IX. Grisea. 



F 



Leaves green above, tomentose beneath; bracts not viscid. 



Bracts, with short spines, the outer not spinulose-ciliate. 35. C spathulatum. 



Bracts, with long spines. ,. , ■ or^ ^ • *« 



Spines of the bracts stout; heads 2.5-3 cm. broad. 39. C. gnseum. 



Spines of the bracts slender; heads about 1.5 cm. broad. 40. C. modestum. 



Leaves loosely floccose on both sides; bracts decidedly viscid. 41. C. canonrens, 



X. Undtjlata. 



Leaves white-tomentose beneath. 



Flowers ochroleucous. ^^ .., ^ , , .. j i -i ^' — ^ ^.u 



Involucral bracts very viscid, with broad glutmous dorsal ridge; divisions of the 



leaves rather few; spines of the bracts short. ^ ^ . , . . , 



Tips of the inner bracts more or less dilate and crisp; involucre of tnetermmal 



head 4-5 cm. m diameter. 42 C. plattense. 



Tips of the inner bracts linear-lanceolate, neither dilated nor crisp; heads 



usuaUy less than 4 cm. in diameter. 

 Bracts verv numerous and small, with small spreading spmes. 

 Stem-leaves deeply pinnately lobed, with rather stout spines. 



Lobes at least of the lower leaves, oblong to rounded-ovate, obtuse. 



43. C Nelsonii, 



Lobes of the leaves lanceolate or linear-lanceolate, acute. 

 Heads more than 3 cm. broad; bracts linear-lanceolate. 



44. C. palousense. 



Heads less than 3 cm. broad; middle bracts ovate-lanceolate or 

 ovate ^^' ^' ^^^cyi. 



Stem-leaves sinuate -dentate or sinuately lobed merely spinulose; 

 heads *> 5-3 cm broad 46. C. nebraskcnse. 



Bracts comparatively' few and broad, with erect spines; leaves sinuate- 

 dentate or slightly lobed. ^ . .^ 41. C. brenjolium. 

 Involucral bracts greenish or yellowish, scarcely viscid with inconspicuous dorsal 

 ridge; division! of the leaves numerous; spmes of the bracts long and slender. 



Flowers rose or purple, rarely white; dorsal viscid ridge not so pronunent. 

 Involucres less than 4 cm. broad. 



Spines of the middle bracts 5-10 mm. long. ,. „ .« ^ ^r-,.nh;m 



Snines of the middle bracts slender and spreadmg. 48. C. acuatum. 



