1008 CARDUACEAE 



liigh; outer bracts narrowly lanceolate, yellowish, often with a darker center and 

 a flat weak spine. Cnicus carlinoides americanus A. Gray. Cniciis aniericanus A. 

 Gray. Carduus americanus Greene. Cirsium ame.ric.anum Daniels, not K. Schum. 

 Carduxis Centaureae Rydb. Mountains: Colo. — Wyo. Submont. — Mont. Jl-Au. 



C. Centaureae X spathulatum. Resembling C . americanum in habit and leaf-form; 

 the bracts heins somewhat erose on the margins as in that species, but scarcely at all 

 dilated, and if so only the innermost, and tipped with the short and broad spines "charac- 

 teristic of C. spathulatum. Colo. 



C. Centaureae X griseum. With the leaves of C. griseum, dark green above, grayish 

 tomentose beneath, the strong and broad spines of the tnvolucral bracts of that species; 

 but most of the bracts are erose on the margins and the inner ones liave dilated tips as 

 in C. americanum. Colo. 



C. acaulescens X Centaureae. ResembUng C. americanum, but the stem lower, heads 

 crowded, involucral bracts elongate and less dilated, leaf-segments more lanceolate, 

 spines stronger, and stem somewhat arachnoid. Colo. 



C. Centaureae Xcoloradense. ResembUng C. americanum, but head larger, hemi- 

 spheric, bracts broader, with less dilated tips, leaves more siiiny, -with more numerous, 

 lanceolate lobes, and slightly arachnoid. Carduus erosus Rydb. Colo. 



17. C. laterifolium (Osterhout) Rydb. Stem 6-8 dm. high; leaves broad, 

 nblong, 1-1.5 dm. long, sessile, ainuculate at the base, short-lobed, glabrous above, 

 white-tomentose beneath, with short and slender spines; involucre 1.5 cm. long 

 and as broad; bracts glabrous, except the shghtly tomentose edges, the outer 

 with short spines, the inner spineless, with narrow, lanceolate tij). Carduus 

 lalerifolius Osterhout. Canons: Colo. Aj. 



18. C. vernale (Osterhout) Cockerell. Stem 2-5 dm. high, slightly tomentose, 

 grooved; leaves narrowly linear in outhne, white-tomentose beneath, green and 

 glabrate or shghtly floccose above, up to 1 dm. long, distantly lobed, with tri- 

 angular-lanceolate lobes; heads scattered, 1.5-2 cm. wide and about as high; 

 bracts all except the innermost with dilated fimbriate tips; flowers bright rose- 

 colored. Carduus vernalis Osterhout. Hills: w Colo. Suh^nont. My-Je. 



19. C. perplexans Rj-db. Stem slender, about 5 dm. high, striate, piirplish, 

 slightly tomentose; lower leaves oblanceolate, the upper lanceolate and clasping, 

 all merely toothed, with weak yellowish spines, glabrous and somewhat glaucous 

 above, rather thinly white-tomentose beneath; heads about 3 cm. high and broad; 

 outer bracts tipped with a short weak spine, the inner tipped with a dilated, 

 deltoid, erose appendage; corolla rose or red-purple. Carduus perplexans Rydb. 

 C. americanus perplexans A. Nels. Mountains: Colo. Submont. Je. 



20. C. Eatoni (A. Gray) B. L. Robinson. Stem 3-6 dm. high, glabrous or 

 slightly arachnoid, angled; leaves linear in outUne, pinnatifid, with short ovate 

 lobes ending in yellow spines, 5-15 cm. long, green on both sides, glabrous or 

 slightly arachnoid on the veins; heads scattered, 3-3.5 cm. high, leafy-bracted; 

 outer bracts spinulose-ciliate and ending in rather stout spines; inner bracts 

 sparingly if at all arachnoid, lance-subulate; corollas rose-purple. Cnicus Eatoni 

 A. Gray. Carduus leiocephalus (D. C. Eat.) Heller. Mountains: Ida. — Utah — 

 Colo. Mont.—Subalp. Jl-S. 



C. Eatoni X olivescens. ResembUng C. Eatoni in habit, but leaves with fewer and 

 deeper lobes and grayish tomentose beneath, and involucres with shorter and weaker 

 spines; differing from C. olivescens in the broader leaf-segments, and narrower bracts, 

 the outer of which are spinulose-ciliate. Utah. 



21. C. clavatum (M. E. Jones) Rydb. Stem 3-7 dm. high, glabrous through- 

 out or nearly so; leaves 2-3 dm. long, pinnatifid, with lanceolate or ovate divi- 

 sions, ending in very short spines, glabrous and shining; heads sohtary or few, 

 hemispheric, 2.5-3 cm. high; bracts glabrous, with a dark spot, all except the 

 innermost with short spines 1-3 mm. long, the outer ones ovate and spinulose- 

 ciliate on the margins, the innermost lance-linear and attenuate into lanceolate 

 or linear-lanceolate, spreading tips; corollas white. Cnicus clavatus M. E. Jones; 

 Carduus clavatus Heller. Wet hillsides: Utah. Suhalp. Au. 



22. C. acaulescens (A. Gray) K. Schum. Biennial or perennial; leaves ob- 

 lanceolate or linear in outline, green, but more or less arachnoid-hairy above, 

 white-tomentose beneath, pinnatifid, with lanceolate lobes tipped with yellow 



t< 

 ^41 



