THISTLE FAMILY 919 



heads 4-6, conglomerate, sessile; involucres 5-6 mm. high; lower portion of the 

 pistillate bracts brownish or greenish; tips dirty white, oblong, obtuse or acut- 

 ish. A. arida viscidula E. Nels. A. viscidula Rydb. High mountains: B.C. 

 Colo. Man. Mont. Alp. Jl. 



24. A. arida E. Nels. Stem 1-2 dm. high, slender; leaves of the rosettes 

 spatulate, acutish, 8-12 cm. long, densely and finely appressed-tomentose on 

 both sides, often conduplicate; stem-leaves often twisted or curved; heads 6-10, 

 sessile, conglomerate; involucres 5-6 mm. high; bracts of the pistillate heads 

 oblong, obtuse, milky-white, those of the staminate heads rounded oval. Dry 

 plains and hills: Mont. N.M. Utah Ida. Submont. Mont. Je-Jl. 



25. A. scariosa E. Nels. Stem 1 dm. high or less; basal leaves spatulate, 

 obtuse or acutish, 1-1.5 cm. long, white-floccose on both sides; stem-leaves oblong 

 or linear-oblong; heads several, somewhat congested; involucres 7-8 mm. high; 

 bracts of pistillate and staminate heads with obovate or oval, obtuse, white tips. 

 Hills: Wyo. Submont. Je. 



26. A. microphylla Rydb. Stem slender, strict, 2-3 dm. high; stem-leaves 

 linear-oblong, small; heads 5-30, conglomerate, 5-6 mm. high and broad; bracts 

 of the pistillate heads linear-oblong to lanceolate, greenish straw-colored, the 

 inner acute, those of the staminate heads oval or elliptic, rounded at the apex. 

 A. parvifolia Greene, not Nutt. A. formosa Greene, a large form. A. solstitialis 

 Lunell, is the staminate plant, which is smaller. Dry hills and plains: Sask. 

 Neb. N.M. B.C. Yukon. Plain Subalp. Je-Jl. 



27. A. bracteosa Rydb. Stem 3-4 dm. high, strict; leaves of the rosettes 

 spatulate, petioled, about 2 cm. long, acutish or mucronate, white-tomentose, 

 with a fine, silky tomentum; stem-leaves about 3 cm. long, oblong or narrowly 

 oblanceolate; heads corymbose; involucres 7-8 mm. high, 5-6 mm. broad; bracts 

 of the pistillate heads oblong or lanceolate, acute, or the inner acuminate, those 

 of the staminate heads oval and obtuse or rounded at the apex. A. parvifolia 

 bracteosa A. Nels. Mountain meadows: Mont. Colo. Submont. Subalp. Je- 



28. A. oxyphylla Greene. Stem 2-4 dm. high; leaves of the rosettes spatu- 

 late-obovate or broadly oblanceolate, densely white-tomentose beneath, less so 

 above; heads many in a rounded corymb; involucres 6-7 mm. high; bracts of the 

 pistillate heads with dull white tips, the outermost ovate, obtusish, the rest 

 lanceolate to linear-lanceolate, acute; staminate plant unknown. Hills and 

 mountains: Mont. Ida. Wyo. Neb. S.D. Plain Submont. My-Jl. 



29. A. obovata E. Nels. Stem 2-3 dm. high; leaves of the rosettes about 

 3 cm. long, obovate-cuneate, permanently tomentose on both sides; stem-leaves 

 small, oblong-linear; heads 3-7, corymbose; involucres about 8 mm. high; bracts 

 of the pistillate heads oblong to linear-lanceolate, with a purplish brown spot, 

 acute or acuminate, or the outermost obtusish. Hills and mountains: Man. 

 S.D. Colo. Alta. Plain Submont. Je-Jl. 



30. A. aprica Greene. Stem low, less than 1.5 dm. high; leaves of the 

 rosettes spatulate or cuneate-oblanceolate, 1-2 cm. long, densely tomentose on 

 both sides; stem-leaves linear, 1 cm. long, acute; heads 3-6, sessile or nearly so, 

 conglomerate; involucres of the pistillate head 7-9 mm. high; bracts numerous, 

 usually with a brown spot and white or pinkish tips, oblong, obtuse, or acutish; 

 involucres of the staminate heads 6-7 mm. high; bracts oval or elliptic-obtuse. 

 (?) A. parvifolia Nutt. A. Holmii, A. obtusa, A. modesta, and A. pumila Greene. 

 Plains, hills, and mountains: Man. Neb. N.M. Utah B.C. Plain Subalp. 

 My-Jl. 



31. A. Howellii Greene. Stem 2-4 dm. high; leaves of the rosettes cuneate- 

 obovate, acute or acutish, 3-5 cm. long, glabrous above, closely silky-tomentose 

 beneath, petioled; stem-leaves small and linear; heads several, corymbose; invo- 

 lucres of the pistillate heads 8-10 mm. high and nearly as broad; outer bracts 

 oblong, the inner linear-lanceolate, very acute, all more or less brownish below. 

 Hillsides and open woods: Alta. Mont. Ida. Wash. B.C. Submont. Mont. 

 My-Jl. 



