THISTLE FAMILY 1005 



Bracts narrow, with weak or slender spines. 



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



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



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



Involucral spines more or less spreading; bracts yellowish; leaves 



shghtly lobed. 15. C. nevadense. 



Involucral spines ascending; bracts greenish; leaves deeply lobed. 



26. C. oUvescens. 

 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. Drummondii. 

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



pale rose. 

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



28. C. magnificum. 

 Heads subsessile and clustered at the end of the stem. 



Plant more or less arachnoid as weU as tomentose; leaves linear in outUne. 



29. C. foliosum. 

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



VIII. PULCHELLA. 



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. 

 Di\isions of the leaves linear to triangular; involucre campanulate. 



Di\'isions of the leaves linear or hnear-lanceolate, often again pinnatifld; 



leaves scarcely decurrent. 32. C. bipinnatum. 



Di\'isions of the leaves ovate or triangular; leaves conspicuoiisly decurrent. 



33. C. calcareum. 

 Di%isions of the leaves semi-orbicular, rounded-ovate; involucre hemispheric. 



34. C. lactucinum. 

 Leaves permanently tomentose, at least beneath. 



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



35. C. spalhulaium. 

 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; involucre narrow. 



37. C. pulchellum. 

 Di\'isions of the leaves broad and short, ovate; coroUas crimson; involucre 

 broad. 38. C. arizonicum. 



IX. Geisea. 

 Leaves green above, tomentose beneath; bracts not -viscid. 



Bracts, with short spines, the outer not spinulose-ciMate. 35. C. spalhulaium. 

 Bracts, with long spines. 



Spines of the bracts stout ; heads 2. ,5-3 cm. broad. 39. C. griseum. 



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. canovirens. 



X. Undxjlata. 

 Leaves white-tomentose beneath. 



Flowers ochroleucous. 



Involucral bracts very A'iscid, with broad glutinous dorsal ridge; divisions of the 

 leavas rather few; spines of the bracts short. 

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



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



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

 usually less than 4 cm. in diameter. 

 Bracts very numeroas and smaU, with small spreading spines. 

 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. 45. C. Tracyi. 



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

 heads 2.5-3 cm. broad. 46. C. nebraskense. 



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

 dentate or shghtly lobed. 47. C. brevifolium. 

 Involucral bracts greenish or yeUowish, scarcely \'iscid, with inconspicuous dorsal 

 ridge; divisions of the leaves numerous; spuies of the bracts long and slender. 



48. C. acuatum. 

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

 Involucres less than 4 cm. broad. 



Spines of the middle bracts .5-10 mm. long. 



Spines of the middle bracts slender and spreading. 48. C. acuatum. 



