THISTLE FAMILY 965 



Lower leaves and often the upper with narrow, again cleft or toothed, spreading divi- 

 sions. 



Heads 25-50-flowered; involucre 4-5 mm. high, 5-S mm. broad. 



Heads erect, borne singly on peduncles 1-12 mm. long; leaves equally tomen- 



tose on both sides. 51. A. floccosa. 



Heads borne in small glom^ules. sessile, only the terminal one erect; leaves 



less tomentose above. 52, A, candicans. 



Heads 20-30-flowered; involucre 3 mm. high, 2.5-3.5 mm. broad. 



53. A. Flodmanii, 



X. DiSCOLORES. 



Licaves densely white-tomentose beneath, loosely floccose above, at least when young. 

 Heads very numerous in a branched leafy panicle; leaves not revolute-marpined. 



54. A. discolor. 

 Heads fewer, usually in a narrow spike-like or racemiform inilorescence ; leaves revo- 



lute-margined. 55. A. Michauxiana, 

 Leaves minutely tomentulose beneath, glabrous above. 



Heads hemispheric, nodding at least in anthesis. 56. A. graveolens. 



Heads campanulate, erect in anthesis. 57. A. tenuis. 



XI. Wrightianae. 



Leaves sparingly pubescent or glabrous, green above. „..,-- 



Heads erect; involucre about 2 mm. broad. 58. A, \%^ngntiu ^ 



Heads nodding; involucre about 3 mm. broad. 59. A. Baken. _ 



Leaves white-tomentose on both sides. 60. A, Carruthti. 



61. A. Abrotanum 



62. A, Bigelovii, 



XII. PONTICAE. 



One species. 



XIII. BiGELOVIANAE. 



One species. 



XIV. Trtdentatae. 



Involucre 4-5 mm. high, 3-5 mm. broad; heads 7-15-flowered (rarely 5- or 6-flowered). 

 Leaves mostly entire; heads numerous in a dense but not spike-like pamcle. 



63. A. carta. 



Leaves, at least some of them, 3-5-toothed at the apex; heads fewer in a narrow spike- 

 like panicle. , ^ _. . ^x, . 

 Plant 1-3 dm. high; branches decumbent or spreadmg at the base. 



64. A. arouscula. 



Plant about 5 dm. high, with erect strict branches. 65. A. spiciformis. 



Involucre 2-4 mm. high, 2-2.5 mm. broad; heads 1-8-flowered. 

 Leaves, at least some of them, 3-toothed at the apex. 



Shrubs 5-50 dm. high; heads numerous m ample pamcles. ^ , .^ , , 



Leaves cuneate. 66. A. tndentata. 



Leaves narrowlv linear-cuneate or linear. 67. A. angusta. 



Shrub 1-4 dm. high; heads fewer. . ^ .x.. ^^«*t,-7-- 



Heads glomerate in dense pamcles; mvolucre turbmate. 62. A. Bigelovxx, 

 Heads in simple, raceme-like panicles; involucre campanulate. 



Heads 7-9-flowered; involucre densely canescent. 64. A. arouscula. 

 Heads 1-6-flowered; involucre nearly glabrous. 68. A. nova. 



Leaves 3-cleft into Unear-Ahform di\^ions. 69. A. tripartita. 



XV. EIGID.^E. . 



One species. 70. A. ngida. 



XVI. Pygmaeae. 



One species. 71. A. pygmaea. 



1 A glauca Pallas. Perennial; stem 3-6 dm. high, silky-pubescent; leaves 

 entire, linear, 2-5 dm. long, 2-5 mm. wide, or with a few linear divisions, silky- 

 canescent : heads small, nmnerous in a large panicle; involucres aboiit 13 mm. 

 broad ■ bracts elliptic, pubescent, scarious-margined ; flowers yellow. Prairies and 

 banks: Man.— Neb.— Colo.— Alta.; Siberia. Plain. Jl-0. 



2 A aromatica A. Nels. Perennial; stems mostly simple, 4-8 dm. high, 

 glabrous; leaves mostly entire, some of the lower 3-cleft, linear, 2-7- cm. lon^ 

 2-i mm. wide; heads numerous, in a large leafy pamcle, nodding; involucres 3-4 

 nmi broad, g abrous; bracts elliptic, dark green with scanous marpns; flowers 

 brown the fertile ones 10-20, the sterile more nmnerous. Mountam vaUeys: 

 Alta.— Colo.— n Calif.— Wash.; n Mex. Submmt. 



3 A dracunculoides Pursh. Perennial; stem 5^15 dm. high, glabrous; 

 leaves narrowly linear, or some 3-cleft with similar divisions, gkbrous 3^7 dm. 



one 1-3 mm wide; heads very numerous, in a compound panicle, nodding; in- 

 volucres broad, glabrous, yeljo^vish f een; bracg dhpt^c obtu^^^^^^ 

 10-20. Prairies and plains: Man.— Mo.— Tex.— Calif.— ±5.<^. t^iam ^uotnont. 



