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 alnft>st 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. 



S. P. Clementis 

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

 luvolucral bracts almost glabrous except the ciliate 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. 



Ba.sal leaf-blades narrowly oblanceolate. H. P. integrifnlia. 

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



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. ienuicaulis. 

 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. hirta. 



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. multicaulis. 

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



2. O. argiUacea. 

 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 mm. high; achenes glabrous. 4. 



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

 Headk radiate. G. 



O. Wardii. 



O. monocephala. 



O. foliosa. 



21. MACRONEMA Nutt. 



Heads radiate; branches glandular, not tomentose. 



Heads small, fastigiate-clusi/ered: disk 5-8 mm. in diameter. 



Leaves broadly obovate, mucronate-ciispidate. 



Leaves oblanceolate, acute or pointed. 

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



Leaves oblanceolate. acute. 



Leaves spatulate, obtuse or mucronate. 

 Heads discoid; branches white-tomontose. 

 Leaves oblong-oblanceolate. 



Outer bracts linear to oblong, acuta. 



Outer bracts broadly oblong, obtuse or mucronate. 

 Leaves linear. 



M. obovatum. 

 M. Watsoni. 



M. suflriiUcosum. 

 M. grindelifoHum. 



M. discoideum 

 M. obtusum. 

 M. lineare. 



22. STENOTUS Nutt. 



Plant glabrous or ouberulent; leaves Arm and evergreen. 



Leaves linear to filiform, 1 mm. wide. 1. 3. stenophyllui. 



Leaves mostly oblanceolate. 

 Bracts lanceolate, acute. 

 Plant puberment. 



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

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



3. S. Andersonii. 

 Plant glabrous, except the scabrous leaf-margins. 



Bases of the basal leaves much 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. falcatus. 



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

 broadly oblanceolate or spatulate. 0. S. laiifolius. 



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



Plant floccose: leaves softer, not evergreen. 8. S. lanuginosus. 



