THISTLE FAMILY 871 



and scabrous-ciliolate on the margins, densely hispidulous-puberulent beneath" 

 inflorescence short-conic; involucre about 3 mm. high; bracts linear-acute- 

 achenes sparingly hispidulous. S. scahriuscula Rydb., in part. Dry soil* Sask' 

 —Mo.— Tex.— Mont. Plain. Jl-S. 



21. S. pruinosa Greene. Stem about 1 m. high; leaves ascending, about 5 

 cm. long, elliptic-lanceolate, acute or acuminate, lightly but evenly serrate, 

 3-ribbed, canescent on both sides, with a dense and soft pubescence; inflorescence 

 short-pyramidal; outer bracts linear-subulate, the inner oblong, lance-obtuse. 

 Plains: Sask. Plain. Au. 



22. S. gilvocanescens (Rydb.) Smyth. Stem slender, 3-6 dm, high, puberu- 

 lent; leaves 3-6 cm. long, sparingly serrate or entire, puberulent-canescent; in- 

 florescence small and dense; heads 3-4 mm. high; bracts narrowly linear, acute; 

 achenes sparingly hairy. Sandy soil: Minn.— Kans.— Utah— Mont. Plain. 

 Jl-Au, 



23. S. Garrettii Rydb. Stem 2-3 dm. high, sparingly puberulent or gla- 

 brous; leaves obovate-spatulate or the upper oval, entire or the lower toothed 

 towards the apex, rather thin, minutely and sparingly scabrous-puberulent, 

 scabrous-ciliolate, 3-6 cm. long; inflorescence more or less leafy, with a few 

 secund branches; heads 5-6 mm. high; bracts lanceolate, acute, yellowish; 

 achenes sparingly hirsute. Canons: Utah— Wyo. Submont, Au. 



24. S. nana Nutt. Stem finely canescent-puberulent, 1-2 dm. (rarely 3 

 dm.) high; basal leaves 2-6 cm. long, petioled, canescent-puberulent, spatulate, 

 rounded at the apex, entire or crenulate; stem-leaves oblanceolate; heads 5-7 

 mm. high; achenes strigose. High dry plains: Mont.— Colo.— Ariz. SuhmonL 

 —Mont. Jl-S. 



25. S. nivea Rydb. Stem 1-2 dm. high, canescent-puberulent; basal leaves 

 2-4 cm. long, short-petioled , obovate-spatulate, rounded at the apex, entire or 

 nearly so, canescent-puberulent, almost velvety and almost white; stem-leaves 

 oblanceolate; heads about 6 mm. high; achenes hirsute-strigose. Dry hillsides; 

 Mont. SuhmonL Jl-Au. 



26. S. pulcherrima A. Nels. Stem 3-8 dm. high, striate, cinereous-puberu- 

 lent; lower leaves narrowly oblanceolate, entire, 6-12 cm. long; upper leaves 

 oblong or linear; all cinereous-puberulent; heads about 6 mm. high; achenes 

 puberulent. S, diffusa A. Nels. Dry plains: Sask.— Minn.— Neb.— Colo.— 

 Ariz. — Alta, Plain — Mont. Jl-S. 



27. S. radulina Rydb. Stem 3-4' dm. high, grayish-puberulcnt; lower 

 leaves obtuse, crenate at the apex, finely puberulent; heads about 4 mm. high; 

 bracts oblong, obtuse, or the inner linear; achenes hirsutulous. Mountains; Utah 

 — Colo. Suhnont. Au. 



28. S. trinervata Greene. Stem decumbent at the base, cinereous-puberu- 

 lent, 3-6 dm. high; leaves oblanceolate, 5-10 cm. long, puberulent, scabrous- 

 ciliolate on the margins, entire or nearly so; heads about 6 mm, high; achenes 

 hispidulous. Plains and hills; S.D. — N.M. — Ariz. — Utah. SuhmonL — MonL Jl-S. 



29. S. mollis Bartl. Stem 2-4 dm. high, cinereous-puberulent, strict, leafy; 

 leaves obovate, oval, or broadly spatulate, or the upper elliptic, canescent, the 

 lower more or less serrate; panicle usually dense and somewhat leafy; heads 5-7 

 mm. high; achenes sparingly hirsutulous. S. nemoralis incana A. Gray. Dry 

 plains: Sask. — ^Tex. — Colo. — Mont. Plain — SuhmonL JI-S. 



30. S. Wardii Britton. Stem 4-10 dm. high, puberulent; leaves lanceolate 

 or ovate-lanceolate, entire or with a few teeth, firm, 5-9 cm. long, pale, usually 

 shining, scabrous-puberulent; panicle narrow, leafy; heads about 8 mm. high; 

 bracts lanceolate, acute, canescent, squarrose. Plains and prairies: Mo. — Ark. 

 — Okla. — w Neb. Plain. Au-0. 



26. PETRADORIA Greene. Rock Goldeneod. 



Low tufted perennial herbs, with a short branched caudex. Leaves alternate, 

 entire, 3-nerved and punctate. Heads small, several, corjTnbose. Involucres 

 cylindraceous; bracts in more or less distinct rows, rigid, somewhat carinate. 



