THISTLE FAMILY 861 



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

 lous-canescent; ligules 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, 

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

 mm. broad; bracts acute or spinulose-tipped; ligules 4-5 mm. long. Dry plains: 

 S.D. la. Tex. N.M. Wyo. Plain. Je-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. Submont. Mont. 



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. 



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. insecticruris. 



Outer bract decidedly shorter. 



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

 aceous. 

 Bracts oblanceolate, abruptly acute; achenes hirsute. 



8. P. dementis. 



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

 Involucral bracts almost glabrous except the ciliate margins, chartace- 



ous at the base with foliaceous 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-villous. 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. lanceolata. 

 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. 



