10 12 CARDUACEAE 



slender tip, the rest lanceolate with yellow spines 3-5 mm. long; corolla straw- 

 colored. Carduus canovirens Rydb. Meadows and slopes: Mont. n Wyo. 

 Ida. Submont. Jl-Au. 



42 C. plattense (Rydb.) Cockerell. Stem 3-7 dm. high, white-tomentose; 

 leaves deeply pinnatifid into oblong divisions, 3-5 cm. long, tipped with slender 

 short yellow spines, densely white-tomentose beneath, more sparingly floccose 

 above; heads 4-5 cm. high; bracts very numerous, yellow, with dark thick glutin- 

 ous backs, all except the innermost broad, ovate, lanceolate, with short yellow 

 spreading spines. Carduus plattensis Rydb. Sandy places: Neb. Colo. 

 Plain. Je-Jl. 



C plattense Xundulatum. Resembling C. plattense in the heads and leaf-form, but 

 the former smaller and with narrower and less viscid bracts. Colo. 



43. C. Nelsonii (Pammel) Rydb. Stem 6-10 dm. high, tomentose; leaves 

 deeply pinnatifid, densely white-tomentose beneath, loosely floccose above; 

 lobes with yellow spines; heads scattered, hemispheric, 3-3.5 cm. high, 3-4 cm. 

 wide; bracts very numerous, all except the innermost lanceolate and tipped with 

 short, flattened, yellow, spreading spines. Cnicus Nelsonii Pammel. Plains: 

 Wyo. Plain. 



44. C. palousense Piper. Stem 3-10 dm. high, tomentose; leaves lanceo- 

 olate, pinnatifid, with entire or 2-cleft lobes, gradually tapering into short spines, 

 white-tomentose beneath, loosely floccose or glabrate above; heads scattered, 

 3-4 cm. high, hemispheric; bracts very numerous, all but the innermost with 

 short slender, terete spines. Carduus palousensis Piper. Meadows: Ore. Ida. 

 Wash. Son. Je-Au. 



45. C. Tracyi Rydb. Stem 3-7 dm. high, loosely floccose; leaves oblanceo- 

 late in outline, divided to near the base, green but slightly flo.ccose above, more or 

 less tomentose beneath; lobes lanceolate to linear-lanceolate, tipped with yellow 

 spines 5-8 mm. long; heads 3-3.5 cm. high and about 3 cm. or less wide; bracts 

 slightly floccose when young, yellowish, the outermost and inner narrowly lanceo- 

 late, the middle ovate-lanceolate, all except the innermost with short spreading 

 spines; innermost bracts attenuate into a linear-lanceolate yellow tip. Carduus 

 Tracyi Rydb. Dry fields: Colo. Utah. Submont. Je-Jl. 



46. C. nebraskense (Britton) Lunell. Stem 3-5 dm. high, tomentose; leaves 

 linear-oblong or lanceolate, white-tomentose beneath, loosely floccose above, 

 entire or irregularly toothed; heads solitary, 3-3.5 cm. high, 3-4 cm. broad; 

 bracts numerous, lanceolate, with short, slender, spreading spines; inner bracts 

 linear-lanceolate, tapering into linear-lanceolate spreading tips. Carduus 

 nebraskensis Britton. Magnesia cliffs: w Neb. Wyo. Plain. Jl. 



47. C. brevifolium Nutt. Stem tomentose, 3-5 dm. high; leaves oblanceo- 

 late or lanceolate, more or less lobed, with triangular lobes and weak yellow 

 spines, white-tomentose beneath, more loosely floccose above; head solitary, 

 about 3 cm. high and 2.5 cm. broad; bracts fewer than in the related species, ovate, 

 with small erect yellow spines, the innermost lance-linear tapering into a slender 

 yellow tip. Hills and ravines: Sask. Mont. Ida. 



48. C. acuatum (Osterhout) Rydb. Stem 8-10 dm. high, striate, floccose; 

 leaves numerous, linear in outline, divided halfway to the midrib, the divisions 

 being again divided into 2 or 3 lanceolate, attenuate, strongly spiny lobes; lower 

 surface densely tomentose, the upper loosely arachnoid, floccose; heads 15-20 

 mm. wide; bracts somewhat floccose on the margins, with a narrow glandular 

 dorsal ridge, all except the innermost armed with slender spreading spines, 5-6 

 mm. long. Carduus acuatus Osterhout. River banks: Colo. Submont. Jl. 



49. C. canescens Nutt. Stem 3-5 dm. high, more or less tomentose; leaves 

 oblong or lanceolate, entire or pinnatifid, with short rounded-oblong lobes, densely 

 white-tomentose beneath, loosely floccose and at last green above; heads scat- 

 tered or sometimes conglomerate, 2-2.5 cm. high, usually less than 2 cm. broad; 

 bracts lanceolate, with very broad, dark glutinous ridges, all except the inner- 

 most with stout ascending or erect spines 5-10 mm. long; corollas rose or rose- 

 purple. Hills and plains: Colo. Wyo. Plain Submont. Je-S. 



