THISTLE FAMILY 271 



Bracts with either a glutinous dorsal ridge or a black spot near the tip. 

 Bracts with a dark spot, but not glutinous; their spines erect. 



IX. Grisea. 

 Bracts with a glutinous dorsal ridge. 



Flowers perfect. X. Undtjlata. 



Flowers dioecious. XI. Ahvensia. 



I. Paeryana. 



Flowers Ught. not pinkish: leaves glabrate. 



Flowers light greenish yellow; leaves arachnoid, but not tomentose beneath. 



1. C. Parryi. 



Flowers whitish; leaves somewhat tomentose beneath. 2. C. araneosum. 



Flowers pinkish; leaves densely white-tomentose beneath. 3. C. scariosum. 



II. Eriocephala. 

 Anthers glabrous. 



Leaves densely tomentose on both sides. 4. C. subniveum. 



Leaves not densely tomentose on both sides. 

 Flowers ochroleucous or white. 



Leaves with very short or no lobes and numerous almost parallel spines along 



the margins, not crisp. 5. C. Kelseyi. 



Leaves with deep divisions, often again lobed, crisp, and with the spines point- 

 ing in various directions. 

 Leaves white-tomentose beneath. 



Involucre densely arachnoid; bracts all narrowly linear-lanceolate'. 

 Heads not nodding, scattered on short branches in the axils of the 



leaves. 6. C. Hookerianum. 



Heads in a terminal dense cluster, at first nodding. 



7. C. scopulorum. 

 Involucres only sUghtly arachnoid; outer bracts lanceolate. 



25. C. oreophilum. 

 Leaves glabrous on both sides; heads clustered in an elongate leafy spike. 



8. C. polyphyllum. 

 Flowers purple or pink. 



Involucre densely arachnoid; bracts rarely spinulose-ciliate. 



Heads 3.5-^ cm. high, 4-6 cm. broad, not densely clustered; corolla red- 

 purple. 9. C. edule. 

 Heads 2.5-3 cm. high and about as broad. 



Heads sessile at the end of the stem; bracts linear-subulate; corolla 



purple. 10. C. Macounii. 



Heads scattered; bracts lance-subulate; corolla pink. 



11. C. T weedy i. 

 Involucres only slightly arachnoid if at aU ; bracts except the innermost spinu- 

 lose-ciliate. 11. C. Ealonii. 

 Anthers pubescent. 12. C. hesperium. 



III. Lanceolata. 



One species. 13. C. kmceolotum. 



IV. Neomexicana. 



Leaves densely white-tomentose; heads 3.5-6 cm. high, 4-8 cm. broad; bracts strongly 

 squarrose, the outer reflexed. 14. C. neomexicanum. 



Leaves loosely floccose; heads 3-3.5 (rarely 4) cm. high, 3.5-5 cm. broad; bracts spreading 

 only in age. 15. C. nevadense. 



V. Caklinoidia. 



Flowers ochroleucous or white; bracts without glutinous ridge. 



Leaves pinnately divided. 16. C. Centaureae. 



Leaves merely sinuately lobed, the upper with broad clasping bases. 



17. C. laterifoHum. 

 Flowers red. 



Bracts without glandular ridge; leaves deeply lobed, with lanceolate divisions. 



18. C. vernale. 

 Bracts with glandular ridge; leaves slightly lobed, with broadly triangular lobes. 



19. C. perplexans. 



VI. Leiocephala. 



Leaves green on both sides, glabrous or arachnoid beneath. 



Leaves crisp and very spiny; involucral bracts very spiny, the outer ones as long as 



the inner; corollas rose or pink. 20. C. Ealoni. 



Leaves almost flat, with weak spines; involucral bracts well imbricate, the outer 

 ones short and with short spines. 21. C. clavalum. 



Leaves tomentose beneath; involucral bracts with strong flat spines. 



39. C. griseum. 



VII. FOLIOSA. 

 Plant acaulescent or nearly so ; heads clustered. 22. C acaulescens. 



Plant distinctly caulescent. 



Inner bracts with scarcely dilated, not erose Unear-lanceolate tips. 

 Heads 3.5-5 cm. high. 



Leaves deeply pinnatifld, with strong spines. 23. C. coloraaense. 



Leaves nearly entire, spinulose-ciliate. 24. C. Bulleri. 



Heads 2-3.5 cm. high. 



