THISTLE FAMILY 861 



parted; involucres 6-8 mm. high; bracts linear-lanceolate, spinulose-tipped, vil- 

 lous-canescent; hgules 6-7 mm. long, bright yellow. A. spinulosus DC. Plains 



and prairies: Sask.— Minn.— Tex.— Ariz.— Alta.; n Mex. Son— Plain— Submont. 

 Je-S. 



^ 7. S. glaberrimus Rydb. Stems several, 1-3 dm. high; leaves rather 

 rigid, about 2 cm. long, bluish green, glabrous, pinnatifid; segments oblong, 

 spmulose-tipped ; heads numerous, corymbose, depressed hemispherical, 8-15 

 mm. broad; bracts acute or spinulose-tipped; Hgules 4^5 mm. long. Dry plains- 

 S.D.— la.— Tex.— N.M.— Wyo. Plain. J^S. ^ . ^ ' 



8. S. puberulus Rydb, Stems less than 1.5 dm. high; leaves pinnatifid or 

 bipinnatifid; segments 1-5 mm. long, spinulose-tipped; heads 8-9 mm. high, 10-12 

 mm. broad; bracts narrowly linear-lanceolate, with small herbaceous tips, finely 

 puberulent; ligules about 20, 8-9 mm. long. Hills: Colo. SuhmonL—MonL 



9. S. turbinellus Rydb. A low and bushy puberulent perennial, 1.5-2 dm. 



high; leaves pinnatifid or the upper reduced and merely toothed; segments nar- 

 row; heads numerous, small, 7-8 mm, high; bracts linear-lanceolate, acute, ap- 

 pressed; ligules 10-15, 7-8 mm. long. Dry plains: Ida. Plain. Au. 



18. PYRROCOMA Nutt. 



_ Perennial herbs, with thick taproots. Leaves alternate, sometimes with 

 spinulose teeth. Heads terminal, or in the axils of the upper leaves, radiate. 

 Involucres hemispheric; bracts more or less foliaceous; receptacle flat, alveolar. 

 Ray-flowers numerous, fertile or sterile; ligules yellow, sometimes not longer than 

 the disk. Disk-flowers yellow, perfect; corollas cylindric, slightly if at all dilated 

 upwards, with short, erect teeth. Appendages of the style-branches subulate- 

 linear, longer than the stigmatic portion. Achenes linear, 3-angled, striate, 

 usually glabrous. Pappus reddish brown or yellow, of numerous rigid bristles. 



r 



Heads apparently discoid, the sterile rays being concealed in the pappus. 



Inner bracts recurved cuspidate. 1. p. subsquarrosa. 



Bracts not recurved cuspidate. 



Bracts oblong or oval; heads hemispheric. 



Leaves and bracts more or less spinulose-toothed, the latter with a narrow 

 scarious margin. 2. P. carthamoides. 



Leaves and bracts not spinulose-toothed, the latter with a broad scarious erose 



margin. 



Pappus sordid; plant almost glabrous. 3. P. rigida. 



Pappus brownish red; plant villous. 4. P. erythropappa. 



Bracts lanceolate; head campanulate-turbinate. ^ 5. P. Cusickii. 



Heads distinctly radiate. 



Bracts except the innermost obtuse, obovate or oblong. 6. P. crocea. 



Bracts mostly acute or acuminate. 

 Plant not glandular. 



Heads large; disk 2 cm. or more in diameter; bracts in about 3 series. 



Bracts almost of the same length. 7. P. inseclicruris. 



Outer bract decidedly shorter. 



Involucre and upper part of stem decidedly villous; bracts wholly foli- 

 aceous. 



Bracts oblanceolate, abruptly acute; achenes hirsute. 



S. P. dementis. 

 Bracts lanceolate, long-acute; achenes glabrous. 9. P. villosa. 

 Involucral bracts almost glabrous except the cihate margins, chartace- 



ous at the base with foUaceous tips. 

 Leaves and stem glabrous, or the latter slightly villous. 



Basal leaf-blades broadly lanceolate. 10. P. lapathifolia. 



Basal leaf-blades narrowly oblanceolate, 11. P. integrifolia. 

 Leaves hirtellous; stem hirsute-viUous. 12. P. scabcrula. 



Heads smaller; disk less than 2 cm. in diameter. 

 Bracts in 2-3 unequal series. 



Leaves 5-15 mm. wide; disk 1-2 cm. wide. 



Inflorescence corymbiform; bracts long-acute. 13. P. lanccolata. 

 Inflorescence racemiform; bracts abruptly acute. 



Stem and bracts more or less white-woolly. 14. P. lagopus. 

 Stem and bracts glabrous or nearly so. 15. P. Vaseyi. 



Leaves 2—4 mm. wide; disk 1 cm. or less wide. 16. P. tenuicaulis. 

 Bracts nearly of the same length. 



Stem-leaves oblanceolate; bracts long-acuminate. 17. P. acuminata. 

 Stem-leaves lanceolate; bracts acute or short-acuminate. 



Plant viUous. 18. P, inuloides. 



Plant, except the upper parts, glabrate in age. 19. P. uniflora. 

 Plant hirsute-villous, decidedly glandular. 20. P. hirta. 



