1008 CARDUACEAE 



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

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

 Gray. Carduus americanus Greene. Cirsium americanum Daniels, not K. Schum. 

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



C. Centaureae X spathulatum. Resembling C. americanum 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. 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 inyolucral 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. Colo. 



C. acaulescens X Centaureae. Resembling 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. Resembling 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 Rydb. 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 slightly tomentose edges, the outer 

 with short spines, the inner spineless, with narrow, lanceolate tip. Carduus 

 laterifolius Osterhout. Canons: Colo. Au. 



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

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

 glabrate or slightly 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. Submont. My-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 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 w r ith 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 outline, 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. 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- 

 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. Subalp. 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 



