THISTLE FAMILY 971 



45. A. longifolia Xutt. Perennial, with a suffruticose base or woody caudex; 

 stem 3-12 dm. high, silvery-tomentose ; leaves linear or lance-Unear, tomentose 

 on both sides, in age greener above, with re volute margins; heads erect, in a 

 narrow raceme-like panicle; involucres 5-6 mm. broad, tomentose; bracts ovate 

 or oval; flowers about 20, yellow. A. natronensis A. Nels., a broad-leaved form. 

 Plains in alkaline soil: Man. — Colo. — Ida. — Wash. Plain. Jl-Au. 



46. A. diversifolia Rydb. White-tomentose perennial, with horizontal 

 rootstock; stem simple, leafy, 5-10 dm. high; leaves densely tomentose on both 

 sides, subsessile, 5-10 cm. long, the lower usually pinnately cleft into 3-5 narrowly 

 lanceolate-acuminate lobes, which are directed forward, the upper or all entire, 

 linear-lanceolate, passing into the bracts of the inflorescence; inflorescence a 

 narrow panicle, 1.5-3 dm. long; heads numerous; involucres 3-4 mm. high and 

 3 mm. broad; bracts oblong or ovate-oblong, scarious-margined, densely villous- 

 tomentose; flowers light vellow. Valleys: Hudson Bay — Neb. — Colo. — CaUf. — 

 B.C. Plain— Suhrnont. 'Jl-S. 



47. A. platyphylla Rydb. Perennial, with a creeping rootstock; stem 4-6 

 dm. high, finely tomentose, simple; lower leaves cuneate-obovate, 5-8 cm. long, 

 with roimded-ovate mucronate lobes above the middle, equally tomentose on 

 both sides; middle leaves similar, but the lobes deeper, triangular or lanceolate; 

 upper leaves ovate or lanceolate, with 3 lanceolate lobes or entire; heads many, 

 in a narrow panicle; involucre hemispheric, 4-5 mm. high and nearly as broad; 

 bracts densely floccose, the outer ovate, acute, the inner oval, obtuse; flowers 

 15-25; corollas yellow. A. ludoviciana latiloba Nutt. Banks: Wash. — Ore. — 

 Mont. 



48. A. Brittonii Rydb. Perennial, with a horizontal rootstock; stem rather 

 stout, 3-6 dm. high, white-floccose ; lower leaves thick, cuneate or oblong-ob- 

 lanceolate, 3-5-lobed, mostly above the middle, densely white-tomentose on 

 both sides, the lobes lanceolate; upper leaves ovate-lanceolate, entire; panicles 

 narrow; involucres 3-4 mm. high, about 2 mm. broad; bracts ovate and densely 

 floccose; flowers about 15, light brown or A'eUow. Hills and plains: Wyo. — Ore. 

 — Ariz. — N.IM.; n Mex. Subtiiont. Au-0. 



49. A. rhizomata A. Nels. Perennial, with a cespitose rootstock; stem 4-6 

 dm. high, white-tomentose; leaves white-tomentose on both sides, 2-4 cm. long, 

 the lower elliptic, oblanceolate, or oblong-cuneate, usually with 3-5 short ovate 

 or lanceolate lobes, the upper lanceolate and entire; heads comparativelj' few, 

 in a narrow, spike-like panicle; branches of the latter short, with 2-6 erect heads; 

 involucre campanulate, about 3.5 mm. high and 3 mm. broad, densely tomen- 

 tose; bracts ovate to elliptic, obtuse; ray- and disk-flowers each 7 or 8; corollas 

 light brown. Hills: Wyo. — N.M. Suhrnont. 



50. A. albula Woot. Perennial, with a rootstock; stem tomentose, 4-10 

 dm. high; lower leaves ovate in outline, 4-5 cm. long, 3-5-lobed, white-tomen- 

 tose on both sides; upper leaves linear to narrowly oblong-lanceolate, 1-3 cm. 

 long, 2-5 mm. broad, usually entire; heads in an open leafy panicle, very numer- 

 ous; involucres 3 mm. high, 2 mm. broad, tomentose; flowers 15-20, yellow. A. 

 microcephala Woot., not Hildebr. Dry plains: Tex. — Colo. — s Calif.; n Mex. 

 Son. Au-0. 



51. A. floccosa Rydb. Perennial, with a creeping rootstock; stem stout, 

 .5-8 dm. high, tomentose; leaves 3-5 cm. long, pinnately divided into oblong, 

 linear, or lanceolate divisions, loosely white-tomentose on both sides, the upper 

 often entire; heads erect, short-peduncled, in a racemiform panicle; involucres 

 5-6 mm. broad, hemispheric; bracts oval, tomentose, scarious-margined; flowers 

 30-60, bro'miish. A. gracilenta A. Nels. A. paucicephala A. Nels., is a form 

 with more entire leaves. Dry banks and mountains: Mont. — Wyo. — Ore. 

 Plain — Mont. Au-S. 



52. A. candicans Rydb. Perennial, with a creeping rootstock; stem stout, 

 5-10 dm. high, tomentose, branched; leaves pinnately or bipinnately divided 

 into oblong divisions, or the upper entire, densely tomentose on both sides; heads 

 numerous, sessile, in small clusters forming interrupted spikes or panicles; invo- 



