49b. Principal involucral bracts with slender spines or none --50. 50a. Pappus feathery; receptacle bristly (summer and autumn) (Thistle) --51. 50b. Pappus not feathery (flowers purple, summer) --59. 51a. Heads subtended by a circle of large leafy bracts (5-15 dm. high; flowers pale-yellow) =Thistle, Cisium spinoissimum.= 51b. Heads not subtended by several leafy bracts --52. 52a. Leaves conspicuously white-woolly on both sides (4-10 dm. high) --53. 52b. Leaves conspicuously white-woolly or brown-woolly below, not above (flowers purple or pink) --54. 52c. Leaves green on both sides (flowers pink or purple, rarely white) --56. 53a. Leaves deeply pinnately parted with linear divisions; flowers almost white =Thistle, Cirsium pitcheri.= 53b. Leaves irregularly pinnatifid; flowers purple-pink =Thistle, Cirsium undulatum.= 54a. Stem-leaves entire or shallowly lobed (1-3 m. high) =Thistle, Cirsium altissimum.= 54b. Stem-leaves obviously pinnatifid (1-2 m. high) --55. 55a. Leaves decurrent on the stem =Thistle, Cirsium lanceolatum.= 55b. Leaves not decurrent =Thistle, Cirsium discolor.= 56a. Outer and middle involucral bracts appressed, pointless or with weak short prickles --57. 56b. Outer and middle bracts erect, not appressed, acuminate into a long slender more or less prickly tip (4-10 dm. high) --58. 57a. Heads numerous 2-2.5 cm. broad, in close clusters (5-12 dm. high) =Canada Thistle, Cirsium arvense.= 57b. Heads few or solitary, 3-5 cm. broad (1-2 m. high) =Thistle, Cirsium muticum.= 58a. Principal bracts with a conspicuous viscid stripe down the middle; heads 6-19 cm. broad, solitary or few =Thistle, Cirsium hillii.= 58b. Principal bracts not viscid =Thistle, Cirsium pumilum.= 59a. Receptacle not bristly; heads 3-5 cm. wide (1-3 m. high; flowers pale-purple, summer) =Cotton Thistle, Onopordum acanthium.= 59b. Receptacle bristly; heads 2-2.5 cm. wide (5-12 dm. high; flowers purple to white, late summer) =Thistle, Carduus crispus.= 60a. Leaves basal; stem-leaves none or reduced to scales (2-8 dm. high; flowers whitish, in spring) --61. 60b. Stem-leaves present; basal leaves present or absent --62. 61a. Leaves toothed or lobed; flower-stalk not scaly =Adenocaulon, Adenocaulon bicolor.= 61b. Leaves deeply cleft; flower-stalk scaly --197a. 62a. Leaves compound or dissected (flowers in summer and autumn) --63. 62b. Leaves merely lobed, never truly compound or dissected --72.