1008 CARDUACEAE 



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

 a flat weak spine. Cnicus carlinoides americanus A. Gray. Cniais americanus A. 

 Gray. Cordinis americanus Greene. Cirsium aynericanum Daniels, not K. Schum. 

 Cardaus Ceniaurtat Rydb. Mountains: Colo.— Wyo. SuhmonL—Moni, Jl-Au. 



C Centaureaexspathulatum. ResembUBg C. mnericanum in habit and leaf-form: 

 the bracts being 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. spaihulatum, Colo. 



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

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

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

 in C. americanum. Golo. 



C acaulescens X Centaureae. Rasembling 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 spiny, with more numerous, 

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



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

 oblong, 1-1.5 dm. long, sessile, auriculate 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 tip. Carduus 

 laterifolius Osterhout. Canons: Colo. Aa. 



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

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

 glabrate or slightlv 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. SuhmonL IVIy-Je. 



19. C, perplexans Rydb. Stem slender, about 5 dm. high, striate, purplish, 

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

 all merely toothed, with weak j^ellowish 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. IVlountains: Colo. Submont. Je. 



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

 slightly arachnoid, angled; leaves hncar in outline, pinnatifid, with short ovate 

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

 sUghtly arachnoid on the veins; heads scattered, 3-3.5 cm. high, leaf y-bracted; 

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

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

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

 Colo. Mont.Suhalp. Jl-S. 



C. Eatoni X olivescens. Resembling 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 solitary 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- 

 cihate on the margins, the innermost lance-Hnear and attenuate into lanceolate 

 or hriear-lanceolate, spreading tips; corollas white. Cnicus clavatum 2vl. E. Jones; 

 Carduus clavatus Heller, Wet hillsides: Utah. Subalp. Au. 



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

 lanceolate or hnear in outhne, green, but more or less arachnoid-hairy above^ 

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



