THISTLE FAMILY 237 



Bracts mostly acute or acuminate. 

 Plant not glandular. 



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



Bracts almost of the same len^^th. 7. P. insecticruris 



Outer bract decidedly shorter. 



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

 aceous. 

 Bracts oblanceolate, abruptly acute; achenes hirsute. 



S. P. Clementis 

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

 Involucral bracts almost glabrous except the ciUate 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. intcgrifnlia. 

 Leaves hirtelloas; stem hirsute-villous. 12. P. scaberula. 



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

 Bracts in 2-3 unequal series. 



Leaves 5-1.5 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 wliite-woolly. 14. P. lagopus. 

 Stem and bracts glabroas or nearly so. 15. P. Vas^eiji. 



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 villous. 18. P. inuloides. 



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

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



19. STENOTOPSIS Rydb. l. S. interior. 



20. OONOPSIS Greene. 



Dwarf; stem less than 1 dm. high; heads 6-10 mm. high. 

 Plant more or less villous; leaves flat; heads radiate. 



Heads 6-8 mm. high; leaves 1-3 cm. long, not exceeding the stem. 



1. O. muhicanlis 

 Heads S-10 mm. high; leaves 4-8 cm. long, often overtopping the stem. 



2. O. argillacea. 

 Plant glabrous; leaves involute; heads discoid. 3. O. Engelmannii. 



Plant robust, 1.5-3 dm. high; heads 15-20 mm. high. 

 Heads discoid. 



Heads clustered. 10-15 ram. high; achenes glabrous. 4. O. Warriii. 



Heads solitary, 15 mm. high or more; achenes glandular. 5. O. rnonoccphala. 



Heads radiate. 6. O. foliosa 



21. MACRONEMA Nutt. 



Heads radiate; branches glandular, not tomentose. 



Heads small, fastiariate-clusiered; disk 5-8 mm. in diameter. 



Leaves broadly obovate, mucronate-cuspidate. 1. M. obovatum. 



Leaves oblanceclat^, acute or pointed. 2. A/. Watsoni. 



Heads larger, solitary: disk 1 cm. or more in diameter. 



Leaves oblanceolate. acute. 3. A/, suflruticosum. 



Leaves spatulate, olituse or mucronate. 4. \l. grindelifolium. 



Heads discoid ; branches white-tomentose. 

 Leaves oblona-oblanceolate. 



Outer bracts linear to oblong, acute. 5. M. discnideum 



Outer bracts broadly oblong, obtuse or mucronate. 6. M. obtusum. 



Leaves linear. 7. M. lineare. 



22. STENOTUS Nutt. 



Plant glabrous or ouberulent; leaves Arm and evergreen. 



Leaves linear to filiform. 1 mm. wide. 1. .'3. slenophyllus-. 



Leaves mostly oblanceolate. 

 Bracts lanceolate, acute. 

 Plant puberuient. 



Bracts in 3 series, broad, with broad scariou? margins. 2. S. acaulis. 

 Bracts in 2 series, narrow, with narrow scarious margins. 



3. S. Andersonii. 

 Plant glabrous, except the scabrous leaf-margin.s. 



Bases of the basal leaves mucli enlarged, somewhat inflated and remaining 

 for years on the short caudal branches; leaf-blades narrowly ob- 

 lanceolate to linear. 

 Stem-leaves oblanceolate, 1-4 cm. long. 4. S. caespitosus. 



Stem-leaves linear, 4-7 cm. long. 5. S. falcatiis. 



Bases of the basal leaves neither much enlarged nor persistent; leaf-blades 

 broadly oblanceolate or spatulate. G. S. lalif alius. 



Bracts oval or oblong, very obtuse. 7. 5. armerioides. 



Plant floccose; leaves softer, not evergreen. 8. S. lanuginosa^. 



