THISTLE FAMILY 973 



61. A. Abrotanum L. A much branched shrub, 5-10 dm. high; louver leaves 

 petioled, 4-6 cm. long, twice pinnately dissected into hnear-fihform divisions, 

 with revolute margins, shghtly tomentose beneath; heads numerous, nodding in 

 leafy panicles with racemiform branches; involucre hemispheric, about 3 mm. 

 high and 5 mm. broad; bracts canescent, the outer linear-hmceolate, the rest 

 broadly oval, scarious; ray-flowers about 10; disk-flowers 15-20. Around dwell- 

 ings: N.B. — Mass.— N.C.^ — Colo.; escaped from cultivation, native of s Eu. and 

 the Orient. 



62. A. Bigelovii A. Gray. Perennial, with a suflFruticose base; stems many, 

 2-3 dm. high, silvery-canescent ; leaves linear-cuneate to oblong, mostly 3-toothed 

 at the apex, about 1 cm. long, silvery-canescent; heads numerous in a th>Tsi- 

 form panicle; involucres canescent, about 2 mm. high and 1.5 mm. broad, 2-4- 

 flowered; flowers yellow, one, or rarely two, of them pistillate. A, petrophila 

 Woot. & Standi. Rocky banks and canons: Tex. — Colo. — Utah— Ariz. Son. 



Au-S. 



63. A. cana Pursh. Shrub, 3-30 dm. high; branches strict, canescent; 

 leaves Unear or lance-linear, acute at both ends, 1-4 cm. long, silvery-canescent 

 on both sides, or the lower with 2-3 acute teeth or lobes at the apex; heads 

 glomerate, in a leafy panicle ; involucres 5-9-flowered ; outer bracts linear or subulate, 

 the inner oval, aU more or less tomentose; flowers yellowish. A. columbiana 

 Nutt. Plains and hills: Sask. — Colo. — Utah— Ore.—Mont. Plain — Mont, Au-S. 



64. A. arbuscula Nutt. Low shrub, 1-3 dm. high; branches slender, canes- 

 cent; leaves short-cuneate or flabelliform, 3-lobed or 3-parted, 5-^12 mm. long, 

 silvery-canescent, or the uppermost entire; heads rather few, in a spike- or raceme- 

 like panicle; involucres about 4 mm. high and 3 mm. broad, 7-9-flowered; bracts 

 efliptic, at least the outer decidedly tomentose; flowers bro^\-nish. Dry moun- 

 tains and high plains: Wyo.— Calif. — Wash, Submont, — M07U, Je~Au. 



65. A, spiciformis Osterhout. Shrub, 3-10 dm. high; branches somewhat 

 canescent; leaves oblanceolate or cuneate, 1-3.5 cm. long, 3-toothed at the apex 

 or the upper entire, silvery-canescent; heads comparatively few, in a spike- or 

 raceme-like inflorescence; involucres about 6 mm. high and 5 mm. wide, about 

 12-flowered; bracts imbricate, ovate, at least the outer tomentose; flowers bro^Ti- 

 ish. A. Rolhrockii A. Gray, in part. Dry plains: Colo. — Utah. Son.— Mont. 



Au-S. 



66. A, tridentata Nutt, Shrub, 1-4 m. high, much branched; bark of the 

 old stems shreddy; branches erect, silvery-canescent; leaves cuneate, 1-2 cm. 

 long, 3-toothed (rarely 4-7-toothed) at the apex, or the upper linear-cimeate and 

 entire silvery-canescent; heads paniculate, numerous; involucres well imbricate, 

 about' 4 mm. long and 2 mm. wide, 5-8-flowered; bracts oval-elliptic, at least 

 the outer densely tomentose; flowers yellow or brownish. Dry plams and hills: 

 Neb.— Colo.— Cahf.— B.C. Plain— MonL Jl-0. 



67 A angusta Rydb. A shrub, 10-12 dm. high, with erect branches; 

 leaves canescent, 2-4 cm. long, 1-4 mm. wide, Hnear and entire or linear-cuneate 

 and merely 3-toothed at the apex; heads numerous, clustered m leafy panicles; 

 involucre 3 5-4 mm. high, 2 mm. broad; the outer bracts thick, ovate, less than 

 one-fourth as long as the innermost; inner bracts oblong, obtuse, scanous-naar- 

 gmed; flowers 4-6. A. tridentata angustifoUa A. Gray. Plams: W ash.— Ida. 

 — Nev. — n Calif. Son. 



68 A nova A. Nels. Undershrub, 1-3 dm. high; branches slightly tomen- 

 tose, strict; leaves narrowly cuneate, 0.5-2 cm. long, 3.toothed at the apex, finely 

 silvery-canescent; heads numerous, in a narrow, racemiform panicle; involucres 

 3-4 mm. high, scarcely 2 mm. broad, 2-4-flowered; bracts well imbricate g a- 

 bmtTS slightly puberulent, efliptic; flowers light brown^ Plams and table- 

 lands: Mont-N,M.-Ariz.-Ida. Suhmmt.-Mont. Au-O 



69. A. tripartita Rydb. Shrub or undershrub, 2-6 dm. high; branches 

 canescent- leaves 3-cleft or 3-parted or the upper entire, silyery-canescent; 

 SdS or loSrnarrowly linear; heads numerous, in a leafy panicle ; mvolucres 

 ?u.^,^.^ .""Ll^ L T^m broad. 3-6-flowered; bracts weU imbricate, the 



